Light-emitting element, light-emitting device, electronic device, and lighting device

ABSTRACT

A novel light-emitting element is provided. A light-emitting element with a long lifetime is provided. A light-emitting element with high emission efficiency is provided. A novel organic compound is provided. A novel organic compound having a hole-transport property is provided. A novel hole-transport material is provided. A hole-transport material including an organic compound having a substituted or unsubstituted benzonaphthofuran skeleton and a substituted or unsubstituted amine skeleton is provided. A light-emitting element using the hole-transport material is provided. An organic compound in which an amine skeleton including two aromatic hydrocarbon groups having 6 to 60 carbon atoms is bonded to the 6- or 8-position of the benzonaphthofuran skeleton is provided.

TECHNICAL FIELD

One embodiment of the present invention relates to a light-emittingelement, a display module, a lighting module, a display device, alight-emitting device, an electronic device, and a lighting device. Notethat one embodiment of the present invention is not limited to the abovetechnical field. The technical field of one embodiment of the inventiondisclosed in this specification and the like relates to an object, amethod, or a manufacturing method. Furthermore, one embodiment of thepresent invention relates to a process, a machine, manufacture, or acomposition of matter. Specifically, examples of the technical field ofone embodiment of the present invention disclosed in this specificationinclude a semiconductor device, a display device, a liquid crystaldisplay device, a light-emitting device, a lighting device, a powerstorage device, a memory device, an imaging device, a method for drivingany of them, and a method for manufacturing any of them.

BACKGROUND ART

Light-emitting elements (organic EL elements) including organiccompounds and utilizing electroluminescence (EL) have been put to morepractical use. In the basic structure of such a light-emitting element,an organic compound layer containing a light-emitting material (an ELlayer) is provided between a pair of electrodes. Carriers are injectedby application of voltage to the element, and light emission can beobtained from the light-emitting material by using the recombinationenergy of the carriers.

The light-emitting elements are self-luminous elements and thus haveadvantages over liquid crystal displays, such as high visibility and noneed for backlight when used as pixels of a display, and are suitable asflat panel display elements. In addition, it is also a great advantagethat a display including such light-emitting elements can bemanufactured as a thin and lightweight display. Furthermore, anextremely high response speed is also a feature thereof.

In such light-emitting elements, light-emitting layers can besuccessively formed two-dimensionally, so that planar light emission canbe obtained. This feature is difficult to realize with point lightsources typified by incandescent lamps and LEDs or linear light sourcestypified by fluorescent lamps. Thus, light-emitting elements also havegreat potential as planar light sources applied to lighting devices andthe like.

Displays or lighting devices including light-emitting elements can besuitably used for a variety of electronic devices as described above,and research and development of light-emitting elements have progressedfor higher efficiency or longer lifetime.

An organic compound having an acceptor property is a material for ahole-injection layer that is used to facilitate the injection ofcarriers, particularly holes, into an EL layer. The organic compoundhaving an acceptor property can be easily deposited by evaporation andthus is suitable for mass production and has become widely used.However, the injection of holes into an EL layer is difficult when theLUMO level of the organic compound having an acceptor property isdistanced from the HOMO level of an organic compound included in ahole-transport layer. In contrast, when the HOMO level of the organiccompound included in the hole-transport layer is raised so as to becloser to the LUMO level of the organic compound having an acceptorproperty, the difference between the HOMO level of the light-emittinglayer and the HOMO level of the organic compound included in thehole-transport layer is large, causing difficulty in hole injection fromthe hole-transport layer into a host material in the light-emittinglayer even when holes can be injected into the EL layer.

In a structure disclosed in Patent Document 1, a hole-transport materialwhose HOMO level is between the HOMO level of a first hole-injectionlayer and the HOMO level of a host material is provided between alight-emitting layer and a first hole-transport layer in contact withthe hole-injection layer.

Although the characteristics of light-emitting elements have beenimproved remarkably, advanced requirements for various characteristicsincluding efficiency and durability are not yet satisfied.

REFERENCE Patent Document

-   [Patent Document 1] PCT International Publication No. WO2011/065136

DISCLOSURE OF INVENTION

In view of the above, an object of one embodiment of the presentinvention is to provide a novel light-emitting element. Another objectof one embodiment of the present invention is to provide alight-emitting element with a long lifetime. Another object of oneembodiment of the present invention is to provide a light-emittingelement with high emission efficiency. Another object of one embodimentof the present invention is to provide a novel organic compound. Anotherobject of one embodiment of the present invention is to provide a novelorganic compound having a hole-transport property. Another object of oneembodiment of the present invention is to provide a novel hole-transportmaterial.

Another object of one embodiment of the present invention is to providea highly reliable light-emitting device, electronic device, and displaydevice. Another object of one embodiment of the present invention is toprovide a low-power-consumption light-emitting device, electronicdevice, and display device.

It is only necessary that at least one of the above-described objects beachieved in the present invention.

One embodiment of the present invention is a hole-transport materialincluding an organic compound having a substituted or unsubstitutedbenzonaphthofuran skeleton and a substituted or unsubstituted amineskeleton.

Another embodiment of the present invention is a hole-transport materialincluding an organic compound having a substituted or unsubstitutedbenzonaphthofuran skeleton and one substituted or unsubstituted amineskeleton.

Another embodiment of the present invention is the hole-transportmaterial with either of the above structures, in which the amineskeleton is bonded to the 6- or 8-position of the benzonaphthofuranskeleton.

Another embodiment of the present invention is the hole-transportmaterial with any of the above structures, in which thebenzonaphthofuran skeleton is directly bonded to a nitrogen atom of theamine skeleton.

Another embodiment of the present invention is a light-emitting elementincluding an anode, a cathode, and an EL layer. The EL layer includes alight-emitting layer and is positioned between the anode and thecathode. The EL layer includes the hole-transport material according toany one of the above.

Another embodiment of the present invention is a light-emitting elementincluding an anode, a cathode, and an EL layer. The EL layer ispositioned between the anode and the cathode, and includes alight-emitting layer and a hole-transport layer. The hole-transportlayer is positioned between the light-emitting layer and the anode, andincludes the hole-transport material according to any one of the above.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the light-emittinglayer includes a light-emitting material and the hole-transportmaterial.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the light-emittinglayer further includes an electron-transport material.

Another embodiment of the present invention is an organic compoundrepresented by General Formula (G1).

Note that in General Formula (G1), R¹ to R⁸ independently represent anyone of hydrogen, a hydrocarbon group having 1 to 6 carbon atoms, acyclic hydrocarbon group having 3 to 6 carbon atoms, an alkoxy grouphaving 1 to 6 carbon atoms, a cyano group, halogen, a haloalkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms. One of A and B representsa group represented by General Formula (g1) and the other represents anyone of hydrogen, a cyclic hydrocarbon group having 3 to 6 carbon atoms,an alkoxy group having 1 to 6 carbon atoms, a cyano group, halogen, ahaloalkyl group having 1 to 6 carbon atoms, a hydrocarbon group having 1to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms.

Note that in General Formula (g1), Ar¹ and Ar² independently representany one of a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 60 carbon atoms and a group represented by General Formula(g2). In the case where Ar¹ and Ar² are each an aromatic hydrocarbongroup having 6 to 60 carbon atoms and include a substituent, thesubstituent includes a benzonaphthofuranyl group and a dinaphthofuranylgroup.

Note that in General Formula (g2), R¹¹ to R¹⁸ independently representany one of hydrogen, a hydrocarbon group having 1 to 6 carbon atoms, acyclic hydrocarbon group having 3 to 6 carbon atoms, an alkoxy grouphaving 1 to 6 carbon atoms, a cyano group, halogen, a haloalkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms. One of Z¹ and Z² isbonded to a nitrogen atom in General Formula (g1) and the otherrepresents any one of hydrogen, a cyclic hydrocarbon group having 3 to 6carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group,halogen, a haloalkyl group having 1 to 6 carbon atoms, a hydrocarbongroup having 1 to 6 carbon atoms, and a substituted or unsubstitutedaromatic hydrocarbon group having 6 to 60 carbon atoms.

Another embodiment of the present invention is the organic compound withany of the above structures, in which the group represented by GeneralFormula (g1) is a group represented by General Formula (g3).

Note that in General Formula (g3), Ar³ and Ar⁴ independently representany one of a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 60 carbon atoms, a substituted or unsubstitutedbenzonaphthofuranyl group, and a substituted or unsubstituteddinaphthofuranyl group. Ar⁵ and Ar⁶ independently represent asubstituted or unsubstituted divalent aromatic hydrocarbon group having6 to 54 carbon atoms, and n and m independently represent 0 to 2. Notethat the sum of carbon atoms of Ar³ and Ar⁵ is less than or equal to 60,and the sum of carbon atoms of Ar⁴ and Ar⁶ is less than or equal to 60.

Another embodiment of the present invention is the organic compound withany of the above structures, in which Ar³ and Ar⁴ independentlyrepresent any one of a substituted or unsubstituted phenyl group, asubstituted or unsubstituted naphthyl group, a substituted orunsubstituted anthracenyl group, and a substituted or unsubstitutedpyrenyl group.

Another embodiment of the present invention is the organic compound withany of the above structures, in which Ar⁵ and Ar⁶ independentlyrepresent any one of a substituted or unsubstituted phenylene group, asubstituted or unsubstituted naphthylene group, a substituted orunsubstituted anthracenylene group, and a substituted or unsubstitutedpyrenylene group.

Another embodiment of the present invention is the organic compound withany of the above structures, in which Ar³ and Ar⁴ are each a phenylgroup.

Another embodiment of the present invention is the organic compound withany of the above structures, in which Ar⁵ and Ar⁶ are each a phenylenegroup.

Another embodiment of the present invention is the organic compound withany of the above structures, in which one of n and m is 1 and the otheris 0.

Another embodiment of the present invention is a light-emitting elementincluding an anode, a cathode, and an EL layer. The EL layer ispositioned between the anode and the cathode. The EL layer includes theorganic compound with any of the above structures.

Another embodiment of the present invention is a light-emitting elementincluding an anode, a cathode, and an EL layer. The EL layer ispositioned between the anode and the cathode, and includes alight-emitting layer. The light-emitting layer includes the organiccompound with any of the above structures.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the light-emittinglayer further includes a light-emitting material.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the light-emittinglayer further includes a material having an electron-transport property.

Another embodiment of the present invention is a light-emitting elementincluding an anode, a cathode, and an EL layer. The EL layer ispositioned between the anode and the cathode. The EL layer includes alight-emitting layer and a hole-transport layer. The hole-transportlayer is positioned between the light-emitting layer and the anode. Thehole-transport layer includes the organic compound with any of the abovestructures.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the EL layer furtherincludes a hole-injection layer, the hole-injection layer is in contactwith the anode and the hole-transport layer, and the hole-injectionlayer includes an organic compound having an acceptor property.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the organic compoundhaving an acceptor property is2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the hole-transportlayer includes a first layer, a second layer, and a third layer, thefirst layer is positioned between the hole-injection layer and thesecond layer, the third layer is positioned between the second layer andthe light-emitting layer, the first layer is in contact with thehole-injection layer, the third layer is in contact with thelight-emitting layer, the first layer includes a first hole-transportmaterial, the second layer includes the organic compound, the thirdlayer includes a third hole-transport material, the light-emitting layerincludes a host material and a light-emitting material, the HOMO levelof the organic compound is deeper than the HOMO level of the firsthole-transport material, the HOMO level of the host material is deeperthan the HOMO level of the organic compound, and the difference betweenthe HOMO level of the organic compound and the HOMO level of the thirdhole-transport material is less than or equal to 0.3 eV.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the HOMO level of thefirst hole-transport material is greater than or equal to −5.4 eV.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the differencebetween the HOMO level of the first hole-transport material and the HOMOlevel of the organic compound is less than or equal to 0.3 eV.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the differencebetween the HOMO level of the organic compound and the HOMO level of thethird hole-transport material is less than or equal to 0.2 eV.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the differencebetween the HOMO level of the first hole-transport material and the HOMOlevel of the organic compound is less than or equal to 0.2 eV.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the HOMO level of thelight-emitting material is higher than the HOMO level of the hostmaterial.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the HOMO level of thethird hole-transport material is deeper than or equal to the HOMO levelof the host material.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the light-emittingmaterial is a fluorescent substance.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the light-emittingmaterial emits blue fluorescence.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the light-emittingmaterial is a condensed aromatic diamine compound.

Another embodiment of the present invention is the light-emittingelement with any of the above structures, in which the light-emittingmaterial is a diaminopyrene compound.

Another embodiment of the present invention is a light-emitting deviceincluding the light-emitting element with any of the above structures,and a transistor or a substrate.

Another embodiment of the present invention is an electronic deviceincluding the above light-emitting device, and a sensor, an operationbutton, a speaker, or a microphone.

Another embodiment of the present invention is a lighting deviceincluding the above light-emitting device and a housing.

Note that the light-emitting device in this specification includes animage display device using a light-emitting element. The light-emittingdevice may include a module in which a light-emitting element isprovided with a connector such as an anisotropic conductive film or atape carrier package (TCP), a module in which a printed wiring board isprovided at the end of a TCP, and a module in which an integratedcircuit (IC) is directly mounted on a light-emitting element by a chipon glass (COG) method. The light-emitting device may also be included inlighting equipment and the like.

According to one embodiment of the present invention, a novellight-emitting element can be provided. A light-emitting element with along lifetime can be provided. A light-emitting element with highemission efficiency can be provided. A novel organic compound can beprovided. A novel organic compound having a hole-transport property canbe provided. A novel hole-transport material can be provided.

According to another embodiment of the present invention, a highlyreliable light-emitting device, electronic device, and display devicecan be provided. A low-power-consumption light-emitting device,electronic device, and display device can be provided.

Note that the description of these effects does not preclude theexistence of other effects. One embodiment of the present invention doesnot necessarily achieve all the effects listed above. Other effects willbe apparent from and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C are schematic diagrams of light-emitting elements.

FIGS. 2A and 2B are conceptual diagrams of an active matrixlight-emitting device.

FIGS. 3A and 3B are conceptual diagrams of an active matrixlight-emitting device.

FIG. 4 is a conceptual diagram of an active matrix light-emittingdevice.

FIGS. 5A and 5B are conceptual diagrams of a passive matrixlight-emitting device.

FIGS. 6A and 6B illustrate a lighting device.

FIGS. 7A to 7D illustrate electronic devices.

FIG. 8 illustrates a light source device.

FIG. 9 illustrates a lighting device.

FIG. 10 illustrates a lighting device.

FIG. 11 illustrates in-vehicle display devices and lighting devices.

FIGS. 12A to 12C illustrate an electronic device.

FIGS. 13A to 13C illustrate an electronic device.

FIGS. 14A and 14B show ¹H NMR charts of BnfABP.

FIG. 15 shows an absorption spectrum and an emission spectrum of asolution of BnfABP.

FIG. 16 shows an absorption spectrum and an emission spectrum of a thinfilm of BnfABP.

FIGS. 17A and 17B show ¹H NMR charts of BBABnf.

FIG. 18 shows an absorption spectrum and an emission spectrum of asolution of BBABnf.

FIG. 19 shows an absorption spectrum and an emission spectrum of a thinfilm of BBABnf.

FIG. 20 shows the luminance-current density characteristics of alight-emitting element 1.

FIG. 21 shows the current efficiency-luminance characteristics of thelight-emitting element 1.

FIG. 22 shows the luminance-voltage characteristics of thelight-emitting element 1.

FIG. 23 shows the current-voltage characteristics of the light-emittingelement 1.

FIG. 24 shows the external quantum efficiency-luminance characteristicsof the light-emitting element 1.

FIG. 25 shows an emission spectrum of the light-emitting element 1.

FIG. 26 shows the time dependence of normalized luminance of thelight-emitting element 1.

FIG. 27 shows the luminance-current density characteristics oflight-emitting elements 2 and 3.

FIG. 28 shows the current efficiency-luminance characteristics of thelight-emitting elements 2 and 3.

FIG. 29 shows the luminance-voltage characteristics of thelight-emitting elements 2 and 3.

FIG. 30 shows the current-voltage characteristics of the light-emittingelements 2 and 3.

FIG. 31 shows the external quantum efficiency-luminance characteristicsof the light-emitting elements 2 and 3.

FIG. 32 shows emission spectra of the light-emitting elements 2 and 3.

FIG. 33 shows the time dependence of normalized luminance of thelight-emitting elements 2 and 3.

FIGS. 34A to 34D are cross-sectional views illustrating a method formanufacturing an EL layer.

FIG. 35 is a conceptual diagram illustrating a droplet dischargeapparatus.

FIGS. 36A and 36B show ¹H NMR charts of BBABnf(6).

FIG. 37 shows an absorption spectrum and an emission spectrum of asolution of BBABnf(6).

FIG. 38 shows an absorption spectrum and an emission spectrum of a thinfilm of BBABnf(6).

FIGS. 39A and 39B show ¹H NMR charts of BBABnf(8).

FIG. 40 shows an absorption spectrum and an emission spectrum of asolution of BBABnf(8).

FIG. 41 shows an absorption spectrum and an emission spectrum of a thinfilm of BBABnf(8).

FIG. 42 shows the luminance-current density characteristics oflight-emitting elements 4 and 5.

FIG. 43 shows the current efficiency-luminance characteristics of thelight-emitting elements 4 and 5.

FIG. 44 shows the luminance-voltage characteristics of thelight-emitting elements 4 and 5.

FIG. 45 shows the current-voltage characteristics of the light-emittingelements 4 and 5.

FIG. 46 shows the external quantum efficiency-luminance characteristicsof the light-emitting elements 4 and 5.

FIG. 47 shows emission spectra of the light-emitting elements 4 and 5.

FIG. 48 shows the time dependence of normalized luminance of thelight-emitting elements 4 and 5.

FIG. 49 shows the luminance-current density characteristics oflight-emitting elements 6 and 7.

FIG. 50 shows the current efficiency-luminance characteristics of thelight-emitting elements 6 and 7.

FIG. 51 shows the luminance-voltage characteristics of thelight-emitting elements 6 and 7.

FIG. 52 shows the current-voltage characteristics of the light-emittingelements 6 and 7.

FIG. 53 shows the external quantum efficiency-luminance characteristicsof the light-emitting elements 6 and 7.

FIG. 54 shows emission spectra of the light-emitting elements 6 and 7.

FIG. 55 shows the luminance-current density characteristics of alight-emitting element 8.

FIG. 56 shows the current efficiency-luminance characteristics of thelight-emitting element 8.

FIG. 57 shows the luminance-voltage characteristics of thelight-emitting element 8.

FIG. 58 shows the current-voltage characteristics of the light-emittingelement 8.

FIG. 59 shows the external quantum efficiency-luminance characteristicsof the light-emitting element 8.

FIG. 60 shows an emission spectrum of the light-emitting element 8.

FIG. 61 shows the time dependence of normalized luminance of thelight-emitting element 8.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below in detailwith reference to the drawings. Note that the present invention is notlimited to the following description, and it will be readily appreciatedby those skilled in the art that the modes and details can be changed invarious different ways without departing from the spirit and the scopeof the present invention. Accordingly, the present invention should notbe interpreted as being limited to the content of the embodiments below.

Embodiment 1

The lifetime of a light-emitting element including an organic materialis particularly affected by the properties of a hole-transport materialin some cases. Above all, the transporting properties of thehole-transport material have considerable influence on the lifetime,which differs significantly according to the type of hole-transportmaterial.

The present inventors have found that a hole-transport materialincluding an organic compound having a substituted or unsubstitutedbenzonaphthofuran skeleton and a substituted or unsubstituted amineskeleton has a suitable transporting property and contributes to anincrease in the lifetime of a light-emitting element including thehole-transport material.

In particular, the hole-transport material preferably includes anorganic compound having a substituted or unsubstituted benzonaphthofuranskeleton and one substituted or unsubstituted amine skeleton. Furtherpreferably, the benzonaphthofuran skeleton of the organic compound inthe hole-transport material is a benzo[b]naphtho[1,2-d]furan skeleton,in which case a highly reliable element can be provided. Still furtherpreferably, the hole-transport material includes the organic compound inwhich the amine skeleton is bonded to the 6- or 8-position of thebenzo[b]naphtho[1,2-d]furan skeleton.

The hole-transport material preferably includes an organic compound inwhich a nitrogen atom of an amine skeleton is directly bonded to thebenzonaphthofuran skeleton without a substituent, in which case a highlyreliable light-emitting element can be provided and the hole-transportmaterial has a suitable HOMO level. This hole-transport material, whichincludes the organic compound in which a nitrogen atom of an amineskeleton is directly bonded to the benzonaphthofuran skeleton without asubstituent, is preferable because it exhibits a high hole-transportproperty and a light-emitting element with a low driving voltage can beprovided.

A light-emitting element using the hole-transport material for an ELlayer can have a long lifetime.

FIGS. 1A to 1C illustrate light-emitting elements of one embodiment ofthe present invention. The light-emitting elements of one embodiment ofthe present invention each include an anode 101, a cathode 102, and anEL layer 103 using the aforementioned hole-transport material includingthe organic compound. The EL layer 103 includes a light-emitting layer113 and may also include a hole-transport layer 112. The light-emittinglayer 113 includes a light-emitting material and a host material, andlight is emitted from the light-emitting material in the light-emittingelement of one embodiment of the present invention. The hole-transportmaterial of one embodiment of the present invention may be included inone or both of the light-emitting layer 113 and the hole-transport layer112.

Note that FIGS. 1A to 1C additionally illustrate a hole-injection layer111, an electron-transport layer 114, and an electron-injection layer115; however, the structure of the light-emitting element is not limitedthereto.

The hole-transport material can also be used as a host material.Furthermore, the hole-transport material and an electron-transportmaterial may be deposited by co-evaporation so that an exciplex isformed of the electron-transport material and the hole-transportmaterial. The exciplex having an appropriate emission wavelength allowsefficient energy transfer to the light-emitting material, achieving alight-emitting element with a high efficiency and a long lifetime.

The above hole-transport material exhibits a good hole-transportproperty and therefore is suitable for the hole-transport layer 112. Inparticular, the hole-transport material is preferably used in the casewhere the hole-injection layer 111 is provided between thehole-transport layer 112 and the anode 101 and includes an organiccompound having an acceptor property, which facilitates the injection ofholes from the electrode.

In the case where the injection of holes is performed using the organiccompound having an acceptor property, a compound included in thehole-transport layer 112 in contact with the hole-injection layer 111 ispreferably a hole-transport material with a relatively shallow HOMOlevel in order to facilitate the extraction of electrons by the organiccompound having an acceptor property. However, holes cannot be easilyinjected into the light-emitting layer 113 from the hole-transportmaterial with a relatively shallow HOMO level, and when thelight-emitting layer 113 is formed in contact with the hole-transportlayer 112 made of the hole-transport material with a relatively shallowHOMO level, carriers are accumulated at their interface, causing adecrease in the lifetime and efficiency of the light-emitting element.Thus, a layer containing the organic compound of one embodiment of thepresent invention is provided between the light-emitting layer 113 andthe hole-transport material with a relatively shallow HOMO level, inwhich case holes can be easily injected into the light-emitting layerand the lifetime and efficiency of the light-emitting element can beimproved.

That is, the hole-transport layer 112 includes a first hole-transportlayer 112-1 and a second hole-transport layer 112-2 from the side of thehole-injection layer 111, and the first hole-transport layer 112-1contains a first hole-transport material whereas the secondhole-transport layer 112-2 contains the hole-transport material of oneembodiment of the present invention. The HOMO level of thehole-transport material of one embodiment of the present invention isdeeper than the HOMO level of the first hole-transport material,achieving a light-emitting element with a long lifetime and a highefficiency. Note that the HOMO level of the first hole-transportmaterial is preferably greater than or equal to −5.4 eV, in which caseelectrons can be easily extracted from the organic compound having anacceptor property.

Preferably, the difference between the HOMO level of the firsthole-transport material and the HOMO level of the hole-transportmaterial of the present invention is less than or equal to 0.3 eV, morepreferably less than or equal to 0.2 eV, in which case holes can beeasily injected from the first hole-transport layer 112-1 to the secondhole-transport layer 112-2.

The hole-transport layer 112 may further include a third hole-transportlayer 112-3 between the second hole-transport layer 112-2 and thelight-emitting layer, and the third hole-transport layer 112-3 maycontain a third hole-transport material. In that case, the HOMO level ofthe third hole-transport material is preferably deeper than the HOMOlevel of the hole-transport material of one embodiment of the presentinvention included in the second hole-transport layer 112-2, and thedifference in the HOMO level is preferably less than or equal to 0.3 eV,more preferably less than or equal to 0.2 eV.

The HOMO level of the third hole-transport material is preferably deeperthan or equal to the HOMO level of the host material, in which caseholes are suitably transported to the light-emitting layer to increasethe lifetime and efficiency.

Note that in the case where the HOMO level of the light-emittingmaterial is shallower (higher) than the HOMO level of the host material,the proportion of holes injected into the light-emitting materialincreases according to the position of the HOMO level of thehole-transport layer, and furthermore, the holes are trapped in thelight-emitting material, which might cause a decreased lifetime due tothe light-emitting region unevenly placed. The structure of thelight-emitting element of the present invention is preferably applied tosuch a case, for example, to a blue fluorescence element. In particular,the structure of the present invention can be preferably used for anaromatic diamine compound that emits excellent blue fluorescence, moreparticularly a pyrenediamine compound and the like, achieving alight-emitting element with excellent lifetime, efficiency, andchromaticity.

Next, examples of specific structures and materials of theaforementioned light-emitting element will be described. As describedabove, the light-emitting element of one embodiment of the presentinvention includes the EL layer 103 that is positioned between the pairof electrodes (the anode 101 and the cathode 102) and has a plurality oflayers. In the EL layer 103, at least the hole-injection layer 111, thehole-transport layer 112, and the light-emitting layer 113 are providedfrom the anode 101 side.

There is no particular limitation on the other layers included in the ELlayer 103, and various layers such as a hole-injection layer, ahole-transport layer, an electron-transport layer, an electron-injectionlayer, a carrier-blocking layer, an exciton-blocking layer, and acharge-generation layer can be employed.

The anode 101 is preferably formed using any of metals, alloys,conductive compounds with a high work function (specifically, a workfunction of 4.0 eV or more), mixtures thereof, and the like. Specificexamples include indium oxide-tin oxide (ITO: indium tin oxide), indiumoxide-tin oxide containing silicon or silicon oxide, indium oxide-zincoxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO).Such conductive metal oxide films are usually formed by a sputteringmethod, but may be formed by application of a sol-gel method or thelike. In an example of the formation method, indium oxide-zinc oxide isdeposited by a sputtering method using a target obtained by adding 1 wt% to 20 wt % of zinc oxide to indium oxide. Furthermore, a film ofindium oxide containing tungsten oxide and zinc oxide (IWZO) can beformed by a sputtering method using a target in which tungsten oxide andzinc oxide are added to indium oxide at 0.5 wt % to 5 wt % and 0.1 wt %to 1 wt %, respectively. Alternatively, gold (Au), platinum (Pt), nickel(Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt(Co), copper (Cu), palladium (Pd), nitride of a metal material (e.g.,titanium nitride), or the like can be used. Graphene can also be used.Note that when a composite material described later is used for a layerin contact with the anode 101 in the EL layer 103, an electrode materialcan be selected regardless of its work function.

Two kinds of stacked layer structure of the EL layer 103 are described:the structure illustrated in FIG. 1A, which includes theelectron-transport layer 114 and the electron-injection layer 115 inaddition to the hole-injection layer 111, the hole-transport layer 112,and the light-emitting layer 113; and the structure illustrated in FIG.1B, which includes the electron-transport layer 114, theelectron-injection layer 115, and a charge-generation layer 116 inaddition to the hole-injection layer 111, the hole-transport layer 112,and the light-emitting layer 113. Materials for forming each layer willbe specifically described below.

The hole-injection layer 111 contains a substance having an acceptorproperty. The structure of one embodiment of the present invention ispreferably used in the case where an organic compound having an acceptorproperty is used. As the organic compound having acceptor property, acompound including an electron-withdrawing group (a halogen group or acyano group), e.g., 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane(abbreviation: F4-TCNQ),3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane, chloranil, or2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN), can be used. The organic compound having an acceptor propertyis preferably a compound in which electron-withdrawing groups are bondedto a condensed aromatic ring having a plurality of hetero atoms, likeHAT-CN, because it is thermally stable. The organic compound having anacceptor property can extract electrons from an adjacent hole-transportlayer (or hole-transport material) by the application of an electricfield.

In the case where the organic compound having an acceptor property isnot used for the hole-injection layer 111, molybdenum oxide, vanadiumoxide, ruthenium oxide, tungsten oxide, manganese oxide, or the like canbe used as the substance having an acceptor property. Alternatively, thehole-injection layer 111 can be formed using a phthalocyanine-basedcompound such as phthalocyanine (abbreviation: H₂Pc) or copperphthalocyanine (CuPc), an aromatic amine compound such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB) orN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD), or a high molecular compound such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS).

Alternatively, a composite material in which a substance having ahole-transport property contains an acceptor substance can be used forthe hole-injection layer 111. By using a composite material in which asubstance having a hole-transport property contains an acceptorsubstance, a material used to form an electrode can be selectedregardless of its work function.

In other words, besides a material having a high work function, amaterial having a low work function can also be used for the anode 101.Examples of the acceptor substance include an organic compound having anacceptor property, such as7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F4-TCNQ), chloranil, or1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation:F6-TCNNQ), and a transition metal oxide. Alternatively, an oxide of ametal belonging to Group 4 to Group 8 in the periodic table can be used.As the oxide of a metal belonging to Group 4 to Group 8 in the periodictable, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide,molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, or thelike is preferably used because their electron-accepting property ishigh. Among these, molybdenum oxide is especially preferable since it isstable in the air and its hygroscopic property is low and is easilytreated.

As the substance having a hole-transport property which is used for thecomposite material, any of a variety of organic compounds such asaromatic amine compounds, carbazole derivatives, aromatic hydrocarbons,and high molecular compounds (e.g., oligomers, dendrimers, or polymers)can be used. Note that the substance having a hole-transport propertywhich is used for the composite material is preferably a substancehaving a hole mobility of 10⁻⁶ cm²/Vs or more. The organic compoundsthat can be used as the substance having a hole-transport property inthe composite material are specifically given below.

Examples of the aromatic amine compounds that can be used for thecomposite material includeN,N′-di(p-tolyl)-N,N′-diphenyl-p-phenylenediamine (abbreviation:DTDPPA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl(abbreviation: DPAB),N,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD), and1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B). Specific examples of the carbazole derivativeinclude 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), 4,4′-di(N-carbazoly)biphenyl (abbreviation:CBP), 1,3,5-tris[4-(N-carbazoly)phenyl]benzene (abbreviation: TCPB),9-[4-(10-phenylanthracen-9-yl)phenyl]-9H-carbazole (abbreviation: CzPA),and 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene. Examplesof the aromatic hydrocarbon include2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),2-tert-butyl-9,10-di(1-naphthyl)anthracene,9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA),2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA),9,10-di(2-naphthyl)anthracene (abbreviation: DNA),9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene(abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene(abbreviation: DMNA),2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene,9,10-bis[2-(1-naphthyl)phenyl]anthracene,2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene,2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9′-bianthryl,10,10′-diphenyl-9,9′-bianthryl,10,10′-bis(2-phenylphenyl)-9,9′-bianthryl,10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl, anthracene,tetracene, rubrene, perylene, and 2,5,8,11-tetra(tert-butyl)perylene.Besides, pentacene, coronene, or the like can be used. The aromatichydrocarbon may have a vinyl skeleton. Examples of the aromatichydrocarbon having a vinyl group are 4,4′-bis(2,2-diphenylvinyl)biphenyl(abbreviation: DPVBi) and9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA).Note that the organic compound of one embodiment of the presentinvention can also be used. In that case, F6-TCNNQ is preferably used asthe acceptor substance.

A high molecular compound such as poly(N-vinylcarbazole) (abbreviation:PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:poly-TPD) can also be used.

By providing a hole-injection layer, a high hole-injection property canbe achieved to allow a light-emitting element to be driven at a lowvoltage.

Note that the hole-injection layer may be formed of the above-describedacceptor material either alone or in combination with another material.In this case, the acceptor material extracts electrons from thehole-transport layer, so that holes can be injected into thehole-transport layer. The acceptor material transfers the extractedelectrons to the anode.

By providing the hole-injection layer 111, a high hole-injectionproperty can be achieved to allow a light-emitting element to be drivenat a low voltage. In addition, the organic compound having an acceptorproperty is easy to use because it is easily deposited by vapordeposition.

The hole-transport layer 112 contains a hole-transport material. Thehole-transport material preferably has a hole mobility of 1×10⁻⁶ cm²/Vsor more. The hole-transport layer 112 preferably includes thehole-transport material of one embodiment of the present invention, inwhich case a light-emitting element with a long lifetime and a highefficiency can be provided.

Particularly when the organic compound having an acceptor property isused for the hole-injection layer 111, at least the hole-injection layer111 consists of two layers of a first and a second hole-transport layer,a first hole-transport material with a relatively shallow HOMO level isused for the first hole-injection layer, and the hole-transport materialof one embodiment of the present invention is used for the secondhole-transport layer; as a result, a light-emitting element with a longlifetime and a high efficiency can be provided.

Although the difference between the LUMO level of the organic compoundhaving an acceptor property and the HOMO level of the firsthole-transport material is not particularly limited because it dependson the strength of the acceptor property of the organic compound havingan acceptor property, holes can be injected when the difference betweenthe levels is less than or equal to approximately 1 eV. Since the LUMOlevel of HAT-CN is estimated to be −4.41 eV by cyclic voltammetrymeasurement, in the case where HAT-CN is used as the organic compoundhaving an acceptor property, the HOMO level of the first hole-transportmaterial is preferably greater than or equal to −5.4 eV. Note that ifthe HOMO level of the first hole-transport material is too high, thehole-injection property for the second hole-transport materialdeteriorates. In addition, since the work function of an anode such asITO is approximately −5 eV, the use of a material whose HOMO level ishigher than −5 eV as the first hole-transport material brings adisadvantage. Therefore, the HOMO level of the first hole-transportmaterial is preferably less than or equal to −5.0 eV.

A third hole-transport layer may be formed between the secondhole-transport layer and the light-emitting layer. The thirdhole-transport layer includes a third hole-transport material.

The first to third hole-transport layers are described above and notrepeatedly described. Note that the hole-transport material included ineach hole-transport layer may be selected from the aforementionedmaterials having hole-transport properties or other various materialshaving hole-transport properties so that the layers have an appropriaterelationship.

The light-emitting layer 113 includes the host material and thelight-emitting material. As the light-emitting material, fluorescentmaterials, phosphorescent materials, substances exhibiting thermallyactivated delayed fluorescence (TADF), or other light-emitting materialsmay be used. Furthermore, the light-emitting layer 113 may be a singlelayer or include a plurality of layers containing differentlight-emitting materials. Note that one embodiment of the presentinvention is more preferably used in the case where the light-emittinglayer 113 emits fluorescence, specifically, blue fluorescence.

Examples of the material that can be used as a fluorescent substance inthe light-emitting layer 113 are described below. Fluorescent substancesother than those given below can also be used.

Examples of the fluorescent substance include5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation:PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine(abbreviation: PAPP2BPy),N,N′-diphenyl-N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6FLPAPrn),N,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn),N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene(abbreviation: TBP),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA),N,N,N′,N′,N″,N″,N″,N″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), coumarin 30,N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPABPhA),9,10-bis(1,1′-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine(abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine(abbreviation: DPhAPhA), coumarin 545T, N,N′-diphenylquinacridone(abbreviation: DPQd), rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile(abbreviation: DCM1),2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCM2),N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:p-mPhTD),7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine(abbreviation: p-mPhAFD),2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTI),2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTB),2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile(abbreviation: BisDCM),2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM),andN,N′-diphenyl-N,N′-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naphtho[1,2-d]furan)-8-aminel](abbreviation:1,6BnfAPrn-03). Condensed aromatic diamine compounds typified bypyrenediamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and1,6BnfAPrn-03 are particularly preferable because of their highhole-trapping properties, high emission efficiency, and highreliability.

Examples of the material that can be used as a phosphorescent substancein the light-emitting layer 113 are as follows.

The examples include organometallic iridium complexes having 4H-triazoleskeletons, such astris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III)(abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]), andtris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPrptz-3b)₃]); organometallic iridium complexeshaving 1H-triazole skeletons, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptzl-mp)₃]) andtris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptzl-Me)₃]); organometallic iridium complexeshaving imidazole skeletons, such asfac-tris[(1-2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]) andtris[3-(2,6-dimethylphenyl-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: [Ir(dmpimpt-Me)₃]); and organometallic iridium complexesin which a phenylpyridine derivative having an electron-withdrawinggroup is a ligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), andbis[2-(4′,6′-difluorophenyOpyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIracac). These are compounds emittingblue phosphorescence and have an emission peak at 440 nm to 520 nm.

Other examples include organometallic iridium complexes havingpyrimidine skeletons, such astris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(mppm)₃]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₃]),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); organometallic iridium complexeshaving pyrazine skeletons, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]); organometallic iridium complexeshaving pyridine skeletons, such astris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation:[Ir(ppy)₃]), bis(2-phenylpyridinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(ppy)₂(acac)]),bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation:[Ir(bzq)₂(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation:[Ir(bzq)₃]), tris(2-phenylquinolinato-N,C^(2′))iridium(III)(abbreviation: [Ir(pq)₃]), andbis(2-phenylquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(pq)₂(acac)]); and rare earth metal complexes such astris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation:[Tb(acac)₃(Phen)]). These are mainly compounds emitting greenphosphorescence and have an emission peak at 500 nm to 600 nm. Note thatorganometallic iridium complexes having pyrimidine skeletons havedistinctively high reliability and emission efficiency and thus areespecially preferable.

Other examples include organometallic iridium complexes havingpyrimidine skeletons, such as(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]),bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(dlnpm)₂(dpm)]); organometallic iridium complexeshaving pyrazine skeletons, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]), and(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]); organometallic iridium complexeshaving pyridine skeletons, such astris(1-phenylisoquinolinato-N,C^(2′))iridium(III) (abbreviation:[Ir(piq)₃]) and bis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(piq)₂(acac)]); platinum complexessuch as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]). These are compounds emitting redphosphorescence and have an emission peak at 600 nm to 700 nm.Furthermore, organometallic iridium complexes having pyrazine skeletonscan provide red light emission with favorable chromaticity.

Besides the above phosphorescent compounds, known phosphorescentmaterials may be selected and used.

Examples of the TADF material include a fullerene, a derivative thereof,acridine, a derivative thereof, an eosin derivative, and ametal-containing porphyrin such as a porphyrin containing magnesium(Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), orpalladium (Pd). Examples of the metal-containing porphyrin include aprotoporphyrin-tin fluoride complex (SnF₂(Proto IX)), amesoporphyrin-tin fluoride complex (SnF₂(Meso IX)), ahematoporphyrin-tin fluoride complex (SnF₂(Hemato IX)), a coproporphyrintetramethyl ester-tin fluoride complex (SnF₂(Copro III-4Me)), anoctaethylporphyrin-tin fluoride complex (SnF₂(OEP)), anetioporphyrin-tin fluoride complex (SnF₂(Etio I)), and anoctaethylporphyrin-platinum chloride complex (PtCl₂(OEP)), which arerepresented by the following structural formulae.

Alternatively, a heterocyclic compound having both of a π-electron richheteroaromatic ring and a π-electron deficient heteroaromatic ring thatis represented by the following structural formulae, such as2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(abbreviation: PIC-TRZ),9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′-phenyl-9H,9′H-3,3′-bicarbazole(abbreviation: PCCzTzn),9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-9H,9′H-3,3′-bicarbazole(abbreviation: PCCzPTzn),2-[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine(abbreviation: PXZ-TRZ),3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole(abbreviation: PPZ-3TPT),3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation:ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(abbreviation: DMAC-DPS), or10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation:ACRSA) can be used. The heterocyclic compound is preferable because ofhaving the π-electron rich heteroaromatic ring and the π-electrondeficient heteroaromatic ring, for which the electron-transport propertyand the hole-transport property are high. Note that a substance in whichthe π-electron rich heteroaromatic ring is directly bonded to theπ-electron deficient heteroaromatic ring is particularly preferably usedbecause the donor property of the π-electron rich heteroaromatic ringand the acceptor property of the π-electron deficient heteroaromaticring are both increased, the energy difference between the S₁ level andthe T₁ level becomes small, and thus thermally activated delayedfluorescence can be obtained with high efficiency. Note that an aromaticring to which an electron-withdrawing group such as a cyano group isbonded may be used instead of the π-electron deficient heteroaromaticring.

As the host material in the light-emitting layer, variouscarrier-transport materials such as materials with an electron-transportproperty and materials with a hole-transport property can be used.

The following are examples of the materials having a hole-transportproperty: compounds having aromatic amine skeletons, such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: mBPAFLP),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBAlBP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBilBP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF), andN-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF); compounds having carbazole skeletons, such as1,3-bis(N-carbazolyl)benzene (abbreviation: mCP),4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP); compounds havingthiophene skeletons, such as4,4′,4″-(benzene-1,3,5-trilyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), and4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and compounds having furan skeletons, such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II)and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II). Among the above materials, the compoundshaving aromatic amine skeletons and the compounds having carbazoleskeletons are preferred because these compounds are highly reliable,have a high hole-transport property, and contribute to a reduction indrive voltage.

The following are examples of materials having an electron-transportproperty: metal complexes such asbis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ);heterocyclic compounds having polyazole skeletons, such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), and2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II); heterocyclic compounds having diazineskeletons, such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine(abbreviation: 4,6mPnP2Pm), and4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II); and heterocyclic compounds having pyridine skeletons,such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation:35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation:TmPyPB). Among the above materials, the heterocyclic compounds havingdiazine skeletons and the heterocyclic compounds having pyridineskeletons are highly reliable and preferred. In particular, theheterocyclic compounds having diazine (pyrimidine or pyrazine) skeletonshave a high electron-transport property and contribute to a decrease indrive voltage.

In the case where a fluorescent substance is used as the light-emittingmaterial, a material having an anthracene skeleton is preferably used asthe host material. The use of a substance having an anthracene skeletonas the host material for the fluorescent substance makes it possible toobtain a light-emitting layer with high emission efficiency and highdurability. Most of materials having an anthracene skeleton have a deepHOMO level; therefore, such a material can be preferably used in oneembodiment of the present invention. Among the substances having ananthracene skeleton, a substance with a diphenylanthracene skeleton, inparticular, a substance with a 9,10-diphenylanthracene skeleton, ischemically stable and thus is preferably used as the host material. Thehost material preferably has a carbazole skeleton because thehole-injection and hole-transport properties are increased; furtherpreferably, the host material has a benzocarbazole skeleton in which abenzene ring is further condensed to carbazole because the HOMO levelthereof is shallower than that of carbazole by approximately 0.1 eV andthus holes enter the host material easily. In particular, the hostmaterial preferably includes a dibenzocarbazole skeleton because theHOMO level thereof is shallower than that of carbazole by approximately0.1 eV so that holes enter the host material easily, the hole-transportproperty is improved, and the heat resistance is increased. Accordingly,a substance that has both a 9,10-diphenylanthracene skeleton and acarbazole skeleton (or a benzocarbazole or dibenzocarbazole skeleton) isfurther preferable as the host material. Note that in terms of thehole-injection and hole-transport properties described above, instead ofa carbazole skeleton, a benzofluorene skeleton or a dibenzo fluoreneskeleton may be used. Examples of such a substance include9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:PCPN) 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation:CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzocarbazole[c,g](abbreviation: cgDBCzPA),6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan(abbreviation: 2mBnfPPA), and9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene(abbreviation: FLPPA). In particular, CzPA, cgDBCzPA, 2mBnfPPA, andPCzPA are preferable choices because of their excellent characteristics.

Note that the light-emitting element of one embodiment of the presentinvention is particularly preferably applied to a light-emitting elementthat emits blue fluorescence.

Note that the host material may be a mixture of plural kinds ofsubstances, and in the case of using a mixed host material, it ispreferable to mix a material having an electron-transport property witha material having a hole-transport property. By mixing the materialhaving an electron-transport property with the material having ahole-transport property, the transport property of the light-emittinglayer 113 can be easily adjusted and a recombination region can beeasily controlled. The ratio of the content of the material having ahole-transport property to the content of the material having anelectron-transport property may be 1:9 to 9:1.

An exciplex may be formed by these mixed materials. It is preferablethat the combination of these materials be selected so as to form anexciplex that emits light with a wavelength overlapping with that of thelowest energy absorption band of the light-emitting material, in whichcase energy is transferred smoothly, light emission can be obtainedefficiently, and the drive voltage is reduced.

The electron-transport layer 114 is a layer containing a substance withan electron-transport property. As the substance having anelectron-transport property, it is possible to use any of theabove-listed substances having electron-transport properties that can beused as the host material.

A layer containing an alkali metal, an alkaline earth metal, or acompound thereof such as lithium fluoride (LiF), cesium fluoride (CsF),or calcium fluoride (CaF₂) may be provided as the electron-injectionlayer 115 between the electron-transport layer 114 and the cathode 102.For example, an electride or a layer that is formed using a substancehaving an electron-transport property and that contains an alkali metal,an alkaline earth metal, or a compound thereof can be used as theelectron-injection layer 115. Examples of the electride include asubstance in which electrons are added at high concentration to calciumoxide-aluminum oxide.

Instead of the electron-injection layer 115, the charge-generation layer116 may be provided (FIG. 1B). The charge-generation layer 116 refers toa layer capable of injecting holes into a layer in contact with thecathode side of the charge-generation layer 116 and electrons into alayer in contact with the anode side thereof when a potential isapplied. The charge-generation layer 116 includes at least a p-typelayer 117. The p-type layer 117 is preferably formed using any of thecomposite materials given above as examples of materials that can beused for the hole-injection layer 111. The p-type layer 117 may beformed by stacking a film containing the above-described acceptormaterial as a material included in the composite material and a filmcontaining a hole-transport material. When a potential is applied to thep-type layer 117, electrons are injected into the electron-transportlayer 114 and holes are injected into the cathode 102 serving as acathode; thus, the light-emitting element operates.

Note that the charge-generation layer 116 preferably includes one orboth of an electron-relay layer 118 and an electron-injection bufferlayer 119 in addition to the p-type layer 117.

The electron-relay layer 118 contains at least the substance having anelectron-transport property and has a function of preventing aninteraction between the electron-injection buffer layer 119 and thep-type layer 117 and smoothly transferring electrons. The LUMO level ofthe substance having an electron-transport property contained in theelectron-relay layer 118 is preferably between the LUMO level of theacceptor substance in the p-type layer 117 and the LUMO level of asubstance contained in a layer of the electron-transport layer 114 thatis in contact with the charge-generation layer 116. As a specific valueof the energy level, the LUMO level of the substance having anelectron-transport property in the electron-relay layer 118 ispreferably higher than or equal to −5.0 eV, more preferably higher thanor equal to −5.0 eV and lower than or equal to −3.0 eV. Note that as thesubstance having an electron-transport property in the electron-relaylayer 118, a phthalocyanine-based material or a metal complex having ametal-oxygen bond and an aromatic ligand is preferably used.

A substance having a high electron-injection property can be used forthe electron-injection buffer layer 119. For example, an alkali metal,an alkaline earth metal, a rare earth metal, or a compound thereof(e.g., an alkali metal compound (including an oxide such as lithiumoxide, a halide, and a carbonate such as lithium carbonate or cesiumcarbonate), an alkaline earth metal compound (including an oxide, ahalide, and a carbonate), or a rare earth metal compound (including anoxide, a halide, and a carbonate)) can be used.

In the case where the electron-injection buffer layer 119 contains thesubstance having an electron-transport property and a donor substance,an organic compound such as tetrathianaphthacene (abbreviation: TTN),nickelocene, or decamethylnickelocene can be used as the donorsubstance, as well as an alkali metal, an alkaline earth metal, a rareearth metal, a compound of the above metal (e.g., an alkali metalcompound (including an oxide such as lithium oxide, a halide, and acarbonate such as lithium carbonate or cesium carbonate), an alkalineearth metal compound (including an oxide, a halide, and a carbonate),and a rare earth metal compound (including an oxide, a halide, and acarbonate)). Note that as the substance having an electron-transportproperty, a material similar to the above-described material used forthe electron-transport layer 114 can be used.

For the cathode 102, any of metals, alloys, electrically conductivecompounds, and mixtures thereof which have a low work function(specifically, a work function of 3.8 eV or less) can be used, forexample. Specific examples of such a cathode material are elementsbelonging to Group 1 or 2 of the periodic table, such as alkali metals(e.g., lithium (Li) and cesium (Cs)), magnesium (Mg), calcium (Ca), andstrontium (Sr), alloys thereof (e.g., MgAg and AlLi), rare earth metalssuch as europium (Eu) and ytterbium (Yb), and alloys thereof. However,when the electron-injection layer is provided between the cathode 102and the electron-transport layer, for the cathode 102, any of a varietyof conductive materials such as Al, Ag, ITO, or indium oxide-tin oxidecontaining silicon or silicon oxide can be used regardless of the workfunction. Films of these conductive materials can be formed by a drymethod such as a vacuum evaporation method or a sputtering method, aninkjet method, a spin coating method, or the like. In addition, thefilms may be formed by a wet method using a sol-gel method, or by a wetmethod using paste of a metal material.

Any of a variety of methods can be used to form the EL layer 103regardless of whether it is a dry process or a wet process. For example,a vacuum evaporation method, a gravure printing method, an offsetprinting method, a screen printing method, an inkjet method, or a spincoating method may be used.

The electrodes or the layers described above may be formed by differentmethods.

The structure of the layers provided between the anode 101 and thecathode 102 is not limited to the above-described structure. Preferably,a light-emitting region where holes and electrons recombine ispositioned away from the anode 101 and the cathode 102 so as to preventquenching due to the proximity of the light-emitting region and a metalused for electrodes and carrier-injection layers.

Furthermore, in order that transfer of energy from an exciton generatedin the light-emitting layer can be suppressed, preferably, thehole-transport layer and the electron-transport layer which are incontact with the light-emitting layer 113, particularly acarrier-transport layer closer to the recombination region in thelight-emitting layer 113, are formed using a material having a widerband gap than the light-emitting material of the light-emitting layer orthe light-emitting material included in the light-emitting layer.

Next, an embodiment of a light-emitting element with a structure inwhich a plurality of light-emitting units are stacked (this type oflight-emitting element is also referred to as a stacked element or atandem element) is described with reference to FIG. 1C. In thislight-emitting element, a plurality of light-emitting units are providedbetween an anode and a cathode. One light-emitting unit hassubstantially the same structure as the EL layer 103 illustrated in FIG.1A. In other words, the light-emitting element illustrated in FIG. 1C isa light-emitting element including a plurality of light-emitting units;each of the light-emitting elements illustrated in FIGS. 1A and 1B is alight-emitting element including a single light-emitting unit.

In FIG. 1C, a first light-emitting unit 511 and a second light-emittingunit 512 are stacked between an anode 501 and a cathode 502, and acharge-generation layer 513 is provided between the first light-emittingunit 511 and the second light-emitting unit 512. The anode 501 and thecathode 502 correspond, respectively, to the anode 101 and the cathode102 illustrated in FIG. 1A, and the materials given in the descriptionfor FIG. 1A can be used. Furthermore, the first light-emitting unit 511and the second light-emitting unit 512 may have the same structure ordifferent structures.

The charge-generation layer 513 has a function of injecting electronsinto one of the light-emitting units and injecting holes into the otherof the light-emitting units when a voltage is applied between the anode501 and the cathode 502. That is, in FIG. 1C, the charge-generationlayer 513 injects electrons into the first light-emitting unit 511 andholes into the second light-emitting unit 512 when a voltage is appliedso that the potential of the anode becomes higher than the potential ofthe cathode.

The charge-generation layer 513 preferably has a structure similar tothat of the charge-generation layer 116 described with reference to FIG.1B. Since the composite material of an organic compound and a metaloxide is superior in carrier-injection property and carrier-transportproperty, low-voltage driving or low-current driving can be achieved.Note that when a surface of a light-emitting unit on the anode side isin contact with the charge-generation layer 513, the charge-generationlayer 513 can also serve as a hole-injection layer in the light-emittingunit and a hole-injection layer is not necessarily formed in thelight-emitting unit.

In the case where the electron-injection buffer layer 119 is provided,the electron-injection buffer layer 119 serves as the electron-injectionlayer in the light-emitting unit on the anode side and thus thelight-emitting unit on the anode side does not necessarily need anelectron-injection layer.

The light-emitting element having two light-emitting units is describedwith reference to FIG. 1C; however, the present invention can besimilarly applied to a light-emitting element in which three or morelight-emitting units are stacked. With a plurality of light-emittingunits partitioned by the charge-generation layer 513 between a pair ofelectrodes as in the light-emitting element according to thisembodiment, it is possible to provide a long-life element which can emithigh luminance light with the current density kept low. Moreover, alow-power-consumption light-emitting device driven at a low voltage canbe manufactured.

Furthermore, when emission colors of light-emitting units are madedifferent, light emission of a desired color can be provided from thelight-emitting element as a whole. For example, in a light-emittingelement having two light-emitting units, the emission colors of thefirst light-emitting unit may be red and green and the emission color ofthe second light-emitting unit may be blue, so that the light-emittingelement can emit white light as the whole element.

The above-described electrodes and layers such as the EL layer 103, thefirst light-emitting unit 511, the second light-emitting unit 512, andthe charge-generation layer can be deposited by a method such as anevaporation method (including a vacuum evaporation method), a dropletdischarge method (also referred to as an ink-jet method), a coatingmethod, or a gravure printing method. A low molecular material, a middlemolecular material (including an oligomer and a dendrimer), or a highmolecular material may be included in the layers and electrodes.

Here, a method for forming an EL layer 786 by a droplet discharge methodis described with reference to FIGS. 34A to 34D. FIGS. 34A to 34D arecross-sectional views illustrating the method for forming the EL layer786.

First, a conductive film 772 is formed over a planarization insulatingfilm 770, and an insulating film 730 is formed to cover part of theconductive film 772 (see FIG. 34A). Then, a droplet 784 is dischargedfrom a droplet discharge apparatus 783 to an exposed portion of theconductive film 772, which is an opening of the insulating film 730, sothat a layer 785 containing a composition is formed. The droplet 784 isa composition containing a solvent and is attached to the conductivefilm 772 (see FIG. 34B).

Note that the step of discharging the droplet 784 may be performed underreduced pressure.

Next, the solvent is removed from the layer 785 containing thecomposition, and the resulting layer is solidified to form the EL layer786 (see FIG. 34C).

The solvent may be removed by drying or heating.

Next, a conductive film 788 is formed over the EL layer 786; thus, alight-emitting element 782 is formed (see FIG. 34D).

When the EL layer 786 is formed by a droplet discharge method asdescribed above, the composition can be selectively discharged;accordingly, waste of material can be reduced. Furthermore, alithography process or the like for shaping is not needed, simplifyingthe process and reducing costs.

The droplet discharge method described above is a general term for ameans to discharge droplets, such as a nozzle with a compositiondischarge opening, or a head with one or a plurality of nozzles.

Next, a droplet discharge apparatus used for the droplet dischargemethod is described with reference to FIG. 35. FIG. 35 is a conceptualdiagram illustrating a droplet discharge apparatus 1400.

The droplet discharge apparatus 1400 includes a droplet discharge means1403. In addition, the droplet discharge means 1403 is equipped with ahead 1405, a head 1412, and a head 1416.

The heads 1405, 1412, and 1416 are connected to a control means 1407that is controlled by a computer 1410; thus, a preprogrammed pattern canbe drawn. The drawing may be conducted at a timing, for example, basedon a marker 1411 formed over a substrate 1402. Alternatively, thereference point may be determined on the basis of an outer edge of thesubstrate 1402. Here, the marker 1411 is detected by an imaging means1404 and converted into a digital signal by an image processing means1409. The digital signal is recognized by the computer 1410, and then, acontrol signal is generated and transmitted to the control means 1407.

An image sensor or the like using a charge coupled device (CCD) or acomplementary metal oxide semiconductor (CMOS) can be used as theimaging means 1404. Note that information about a pattern to be formedover the substrate 1402 is stored in a storage medium 1408, and acontrol signal is transmitted to the control means 1407 based on theinformation, so that each of the heads 1405, 1412, and 1416 of thedroplet discharge means 1403 can be individually controlled. A materialto be discharged is supplied to the heads 1405, 1412, and 1416 frommaterial supply sources 1413, 1414, and 1415, respectively, throughpipes.

Inside the head 1405, a space as indicated by a dotted line 1406 to befilled with a liquid material and a nozzle which is a discharge outletare provided. Although it is not shown, the inside structures of theheads 1412 and 1416 are similar to the inside structure of the head1405. When the heads 1405 and 1412 have different nozzle sizes,different materials with different widths can be dischargedsimultaneously. Each head can discharge and draw a plurality oflight-emitting materials. In the case of drawing over a large area, thesame material can be simultaneously discharged to be drawn from aplurality of nozzles in order to improve throughput. When a largesubstrate is used, the heads 1405, 1412, and 1416 can freely scan thesubstrate in directions indicated by arrows X, Y, and Z in FIG. 35, anda region in which a pattern is drawn can be freely set. Thus, aplurality of the same patterns can be drawn over one substrate.

The step of discharging the composition may be performed under reducedpressure. Also, a substrate may be heated when the composition isdischarged. After discharging the composition, one or both of drying andbaking are performed. Both the drying and baking are heat treatments butdifferent in purpose, temperature, and time period. The steps of dryingand baking are performed under normal or reduced pressure by laserirradiation, rapid thermal annealing, heating using a heating furnace,or the like. Note that the timing of the heat treatment and the numberof times of the heat treatment are not particularly limited. Thetemperature for adequately performing the steps of drying and bakingdepends on the materials of the substrate and the properties of thecomposition.

In the above manner, the EL layer 786 can be formed with the dropletdischarge apparatus.

In the case where the EL layer 786 is formed with the droplet dischargeapparatus, a hole-transport layer can be formed by a wet method using acomposition in which the hole-transport material of the presentinvention is dissolved in a solvent. In that case, the following variousorganic solvents can be used to form a coating composition: benzene,toluene, xylene, mesitylene, tetrahydrofuran, dioxane, ethanol,methanol, n-propanol, isopropanol, n-butanol, t-butanol, acetonitrile,dimethylsulfoxide, dimethylformamide, chloroform, methylene chloride,carbon tetrachloride, ethyl acetate, hexane, cyclohexane, and the like.In particular, less polar benzene derivatives such as benzene, toluene,xylene, and mesitylene are preferable because a solution with a suitableconcentration can be obtained and the hole-transport material of thepresent invention contained in ink can be prevented from deterioratingdue to oxidation or the like. Furthermore, to achieve a uniform film ora film with a uniform thickness, a solvent with a boiling point of 100°C. or higher is preferably used, and more preferably, toluene, xylene,or mesitylene is used.

Note that the above structure can be combined with any of the structuresin this embodiment and the other embodiments as appropriate.

Embodiment 2

In this embodiment, an organic compound of one embodiment of the presentinvention will be described.

Some of the organic compounds described in Embodiment 1, which can beused as the second hole-transport material, are novel compounds andtherefore are embodiments of the present invention. The organic compoundof one embodiment of the present invention will be described below.

The organic compound of one embodiment of the present invention isrepresented by General Formula (G1).

Note that in General Formula (G1), R¹ to R⁸ independently represent anyone of hydrogen, a hydrocarbon group having 1 to 6 carbon atoms, acyclic hydrocarbon group having 3 to 6 carbon atoms, an alkoxy grouphaving 1 to 6 carbon atoms, a cyano group, halogen, a haloalkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms.

Specific examples of R¹ to R⁸ in General Formula (G1) are represented byFormulae (1-1) to (1-40). In the case where R¹ to R⁸ are each asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 60carbon atoms, aromatic hydrocarbon in a skeleton of a substituent arerepresented by Formulae (2-1) to (2-13). Note that there is nolimitation on the site of substitution of the aromatic hydrocarbonrepresented by Formulae (2-1) to (2-13), and a plurality of aromatichydrocarbon groups may be connected to form a skeleton.

Note that in the case where R¹ to R⁸ are each an aromatic hydrocarbongroup including a substituent, the substituent can be any of ahydrocarbon group having 1 to 6 carbon atoms, a cyclic hydrocarbon grouphaving 3 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,a cyano group, halogen, a haloalkyl group having 1 to 6 carbon atoms, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 60carbon atoms, a dibenzofuranyl group, a dibenzothiophenyl group, abenzonaphthofuranyl group, and a benzonaphthothiophenyl group. In thecase where R¹ to R⁸ are each an aromatic hydrocarbon group including asubstituent and the substituent is any of a hydrocarbon group having 1to 6 carbon atoms, a cyclic hydrocarbon group having 3 to 6 carbonatoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group,halogen, and a haloalkyl group having 1 to 6 carbon atoms, specificstructure examples of R¹ to R⁸ are the same as the structuresrepresented by Formulae (1-1) to (1-40), which are shown above asspecific examples of R¹ to R⁸.

In the case where R¹ to R⁸ are each an aromatic hydrocarbon groupincluding a substituent and the substituent is any of a substituted orunsubstituted aromatic hydrocarbon group having 6 to 60 carbon atoms, adibenzofuranyl group, a dibenzothiophenyl group, a benzonaphthofuranylgroup, and a benzonaphthothiophenyl group, specific examples of R¹ to R⁸are represented by Formulae (1-41) to (1-81). In all the substituentsrepresented by Formulae (1-41) to (1-81), there is no limitation on thesite of substitution.

One of A and B represents a group represented by General Formula (g1)and the other represents any one of hydrogen, a cyclic hydrocarbon grouphaving 3 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,a cyano group, halogen, a haloalkyl group having 1 to 6 carbon atoms, ahydrocarbon group having 1 to 6 carbon atoms, and a substituted orunsubstituted aromatic hydrocarbon group having 6 to 60 carbon atoms.Specific examples are the same as those of the substituents R¹ to R⁸.

Note that in General Formula (g1), Ar¹ and Ar² independently representany one of a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 60 carbon atoms and a group represented by General Formula(g2). In the case where Ar¹ and Ar² are each an aromatic hydrocarbongroup having 6 to 60 carbon atoms and include a substituent, thesubstituent includes a benzonaphthofuranyl group and a dinaphthofuranylgroup.

Note that in General Formula (g2), R¹¹ to R¹⁸ independently representany one of hydrogen, a hydrocarbon group having 1 to 6 carbon atoms, acyclic hydrocarbon group having 3 to 6 carbon atoms, an alkoxy grouphaving 1 to 6 carbon atoms, a cyano group, halogen, a haloalkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms. One of Z¹ and Z² isbonded to a nitrogen atom in General Formula (g1) and the otherrepresents any one of hydrogen, a cyclic hydrocarbon group having 3 to 6carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group,halogen, a haloalkyl group having 1 to 6 carbon atoms, a hydrocarbongroup having 1 to 6 carbon atoms, and a substituted or unsubstitutedaromatic hydrocarbon group having 6 to 60 carbon atoms. Note thatspecific examples of R¹¹ to R¹⁸ in the group represented by GeneralFormula (g2) are the same as those of R¹ to R⁸ in the organic compoundrepresented by General Formula (G1). Further, specific examples of oneof Z¹ and Z² that is not bonded to a nitrogen atom in the grouprepresented by General Formula (g1) are the same as those of one of Aand B in the organic compound represented by General Formula (G1) thatis not represented by General Formula (g1). That is, one of Z¹ and Z²that is not bonded to a nitrogen atom in the group represented byGeneral Formula (g1) represents any one of hydrogen, a cyclichydrocarbon group having 3 to 6 carbon atoms, an alkoxy group having 1to 6 carbon atoms, a cyano group, halogen, a haloalkyl group having 1 to6 carbon atoms, a hydrocarbon group having 1 to 6 carbon atoms, and asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 60carbon atoms. Note that specific examples thereof are the same as thoseof the above substituents R¹ to R⁸.

Specific skeleton examples of the aromatic hydrocarbon group having 6 to60 carbon atoms, which can be used as Ar¹ and Ar² in General Formula(g1), are skeletons represented by Structural Formulae (2-1) to (2-13).Note that there is no limitation on the site of substitution and eachgroup may consist of a plurality of skeletons.

Note that in the case where Ar¹ and Ar² in General Formula (g1) are eachan aromatic hydrocarbon group including a substituent, the substituentcan be any of a hydrocarbon group having 1 to 6 carbon atoms, a cyclichydrocarbon group having 3 to 6 carbon atoms, an alkoxy group having 1to 6 carbon atoms, a cyano group, halogen, a haloalkyl group having 1 to6 carbon atoms, a substituted or unsubstituted aromatic hydrocarbongroup having 6 to 60 carbon atoms, a dibenzofuranyl group, adibenzothiophenyl group, a benzonaphthofuranyl group, and abenzonaphthothiophenyl group. In the case where Ar¹ and Ar² are each anaromatic hydrocarbon group including a substituent and the substituentis any of a hydrocarbon group having 1 to 6 carbon atoms, a cyclichydrocarbon group having 3 to 6 carbon atoms, an alkoxy group having 1to 6 carbon atoms, a cyano group, halogen, and a haloalkyl group having1 to 6 carbon atoms, specific structure examples of Ar¹ and Ar² are thesame as the structures represented by Formulae (1-1) to (1-40), whichare shown above as specific examples of R¹ to R⁸ in General Formula(G1).

In the case where Ar¹ and Ar² in General Formula (g1) are each anaromatic hydrocarbon group including a substituent and the substituentis any of a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 60 carbon atoms, a dibenzofuranyl group, a dibenzothiophenylgroup, a benzonaphthofuranyl group, and a benzonaphthothiophenyl group,specific examples of Ar¹ and Ar² are represented by Formulae (1-41) to(1-135). In all the substituents represented by Formulae (1-41) to(1-135), there is no limitation on the site of substitution.

Specific examples of the substituents represented by Formula (g2) are asfollows.

Another embodiment of the present invention is the organic compound inwhich the group represented by General Formula (g1) is a grouprepresented by General Formula (g3).

Note that in General Formula (g3), Ar³ and Ar⁴ independently representany one of a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 60 carbon atoms, a substituted or unsubstitutedbenzonaphthofuranyl group, and a substituted or unsubstituteddinaphthofuranyl group. Ar³ and Ar⁴ are the same as Ar¹ and Ar² inGeneral Formula (g1). Note that the sum of carbon atoms of Ar³ and Ar⁵is less than or equal to 60, and the sum of carbon atoms of Ar⁴ and Ar⁶is less than or equal to 60.

Ar⁵ and Ar⁶ independently represent a substituted or unsubstituteddivalent aromatic hydrocarbon group having 6 to 54 carbon atoms, and nand m independently represent 0 to 2. Note that the sum of carbon atomsof Ar³ and Ar⁵ is less than or equal to 60, and the sum of carbon atomsof Ar⁴ and Ar⁶ is less than or equal to 60. Specific examples of Ar⁵ andAr⁶ are divalent groups having skeletons represented by StructuralFormulae (2-1) to (2-13).

In the organic compound having the above structure, preferably, Ar³ andAr⁴ each represent any one of a substituted or unsubstituted phenylgroup, a substituted or unsubstituted naphthyl group, a substituted orunsubstituted anthracenyl group, and a substituted or unsubstitutedpyrenyl group, which allows the transport layer to have high heatresistance, good film quality, and favorable hole-transport properties.In particular, each of Ar³ and Ar⁴ preferably represents a phenyl groupbecause the layer with favorable hole-transport properties can bedeposited efficiently.

In the organic compound having the above structure, preferably, Ar⁵ andAr⁶ each represent any one of a substituted or unsubstituted phenylenegroup, a substituted or unsubstituted naphthylene group, a substitutedor unsubstituted anthracenylene group, and a substituted orunsubstituted pyrenylene group, which allows the transport layer to havehigh heat resistance, good film quality, and favorable hole-transportproperties. In particular, each of Ar⁵ and Ar⁶ preferably represents aphenylene group because the layer with favorable hole-transportproperties can be deposited efficiently.

In the organic compound having the above structure, particularlypreferably, one of n and m is 1 and the other is 0, in which case a highquality film with favorable hole-transport properties is achieved.

Specific examples of the organic compound with the above structure areshown below.

The above organic compounds can be synthesized by Synthesis Schemes(a-1), (a-2), (b-1), and (b-2) shown below.

A method for synthesizing the organic compound represented by GeneralFormula (G1) is described. In General Formula (G1), R¹ to R⁸independently represent any one of hydrogen, a hydrocarbon group having1 to 6 carbon atoms, a cyclic hydrocarbon group having 3 to 6 carbonatoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group,halogen, a haloalkyl group having 1 to 6 carbon atoms, and a substitutedor unsubstituted aromatic hydrocarbon group having 6 to 60 carbon atoms.One of A and B represents a group represented by General Formula (g1)and the other represents any one of hydrogen, a cyclic hydrocarbon grouphaving 3 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,a cyano group, halogen, a haloalkyl group having 1 to 6 carbon atoms, ahydrocarbon group having 1 to 6 carbon atoms, and a substituted orunsubstituted aromatic hydrocarbon group having 6 to 60 carbon atoms.

Note that in General Formula (g1), Ar¹ and Ar² independently represent asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 60carbon atoms. In the case where Ar¹ and Ar² each include a substituent,the substituent includes a benzonaphthofuranyl group and adinaphthofuranyl group.

Thus, General Formula (G1) can be represented by General Formula (G1-a)or (G1-b). A variety of reactions can be applied to the method forsynthesizing the organic compounds represented by General Formulae(G1-a) and (G1-b). Note that the method for synthesizing the organiccompounds of one embodiment of the present invention represented byGeneral Formulae (G1-a) and (G1-b) is not limited to the followingsynthesis method.

<Method for Synthesizing Organic Compound Represented by General Formula(G1-a)>

The organic compound of one embodiment of the present inventionrepresented by General Formula (G1-a) can be synthesized by SynthesisScheme (a-1) or (a-2) shown below.

That is, a benzonaphthofuran compound (compound 1) is coupled withdiarylamine (compound 2), whereby a benzonaphthofuranylamino compound(G1-a) can be obtained. Alternatively, benzonaphthofuranylamine(compound 3) is coupled with a compound having an aryl skeleton(compound 4), whereby a benzonaphthofuranylamino compound (G1-a) can beobtained. Synthesis Schemes (a-1) and (a-2) are shown below.

In Synthesis Schemes (a-1) and (a-2), R¹ to R⁸ independently representany one of hydrogen, a hydrocarbon group having 1 to 6 carbon atoms, acyclic hydrocarbon group having 3 to 6 carbon atoms, an alkoxy grouphaving 1 to 6 carbon atoms, a cyano group, halogen, a haloalkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms. A represents any one ofhydrogen, a cyclic hydrocarbon group having 3 to 6 carbon atoms, analkoxy group having 1 to 6 carbon atoms, a cyano group, halogen, ahaloalkyl group having 1 to 6 carbon atoms, a hydrocarbon group having 1to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms. Ar¹ and Ar² independentlyrepresent a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 60 carbon atoms. In the case where Ar¹ and Ar² each includea substituent, the substituent includes a benzonaphthofuranyl group anda dinaphthofuranyl group and does not include an amino group.

X¹ and X⁴ independently represent chlorine, bromine, iodine, or atriflate group, and X² and X³ independently represent hydrogen, anorganotin group, or the like.

In the case where the Buchwald-Hartwig reaction using a palladiumcatalyst is employed in Synthesis Schemes (a-1) and (a-2), a palladiumcompound such as bis(dibenzylideneacetone)palladium(0), palladium(II)acetate, [1,1-bis(diphenylphosphino)ferrocene]palladium(II) dichloride,tetrakis(triphenylphosphine)palladium(0), or allylpalladium(II) chloride(dimer) and a ligand such as tri(tert-butyl)phosphine,tri(n-hexyl)phosphine, tricyclohexylphosphine,di(1-adamantyl)-n-butylphosphine,2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl,tri(ortho-tolyl)phosphine, or(S)-(6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diisopropylphosphine)(abbreviation: cBRIDP (registered trademark)), can be used. In thereaction, an organic base such as sodium tert-butoxide, an inorganicbase such as potassium carbonate, cesium carbonate, or sodium carbonate,or the like can be used. In the reaction, toluene, xylene, benzene,tetrahydrofuran, dioxane, or the like can be used as a solvent. Thereagents that can be used in the reaction are not limited to the abovereagents.

In the case where the Ullmann reaction using copper or a copper compoundis performed in Synthesis Schemes (a-1), (a-2), and (b-1), X¹ and X⁴independently represent chlorine, bromine, or iodine, and X² and X³represent hydrogen. Copper or a copper compound can be used for thereaction. Examples of the base used include an inorganic base such aspotassium carbonate. Examples of the solvent that can be used for thereaction include 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone(DMPU), toluene, xylene, and benzene. In the Ullmann reaction, since theobjective product can be obtained in a shorter time and in a higheryield when the reaction temperature is 100° C. or higher; therefore, itis preferable to use DMPU or xylene that has a high boiling temperature.A reaction temperature of 150° C. or higher is further preferred andaccordingly DMPU is more preferably used. The reagents that can be usedfor the reaction are not limited to the above reagents.

<Method for Synthesizing Organic Compound Represented by General Formula(G1-b)>

The organic compound of the present invention represented by GeneralFormula (G1-b) can be synthesized by Synthesis Scheme (b-1) or (b-2)shown below.

That is, a benzonaphthofuran compound (compound 5) is coupled withdiarylamine (compound 6), whereby a benzonaphthofuranylamino compound(G1-b) can be obtained. Alternatively, benzonaphthofuranylamine(compound 7) is coupled with a compound having an aryl skeleton(compound 8), whereby a benzonaphthofuranylamino compound (G1-b) can beobtained. Synthesis Schemes (b-1) and (b-2) are shown below.

In Synthesis Schemes (b-1) and (b-2), R¹ to R⁸ independently representany one of hydrogen, a hydrocarbon group having 1 to 6 carbon atoms, acyclic hydrocarbon group having 3 to 6 carbon atoms, an alkoxy grouphaving 1 to 6 carbon atoms, a cyano group, halogen, a haloalkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms. A represents any one ofhydrogen, a cyclic hydrocarbon group having 3 to 6 carbon atoms, analkoxy group having 1 to 6 carbon atoms, a cyano group, halogen, ahaloalkyl group having 1 to 6 carbon atoms, a hydrocarbon group having 1to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms. Ar¹ and Ar² independentlyrepresent a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 60 carbon atoms. In the case where Ar¹ and Ar² each includea substituent, the substituent includes a benzonaphthofuranyl group anda dinaphthofuranyl group and does not include an amino group.

X¹ and X⁴ independently represent chlorine, bromine, iodine, or atriflate group, and X² and X³ independently represent hydrogen, anorganotin group, or the like.

In the case where the Buchwald-Hartwig reaction using a palladiumcatalyst is employed in Synthesis Schemes (b-1) and (b-2), a palladiumcompound such as bis(dibenzylideneacetone)palladium(0), palladium(II)acetate, [1,1-bis(diphenylphosphino)ferrocene]palladium(II) dichloride,tetrakis(triphenylphosphine)palladium(0), or allylpalladium(II) chloride(dimer) and a ligand such as tri(tert-butyl)phosphine,tri(n-hexyl)phosphine, tricyclohexylphosphine,di(1-adamantyl)-n-butylphosphine,2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl,tri(ortho-tolyl)phosphine, or(S)-(6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diisopropylphosphine)(abbreviation: cBRIDP (registered trademark)), can be used. In thereaction, an organic base such as sodium tert-butoxide, an inorganicbase such as potassium carbonate, cesium carbonate, or sodium carbonate,or the like can be used. In the reaction, toluene, xylene, benzene,tetrahydrofuran, dioxane, or the like can be used as a solvent. Thereagents that can be used in the reaction are not limited to the abovereagents.

In the case where the Ullmann reaction using copper or a copper compoundis performed in Synthesis Schemes (b-1) and (b-2), X¹ and X⁴independently represent chlorine, bromine, or iodine, and X² and X³represent hydrogen. Copper or a copper compound can be used for thereaction. Examples of the base used include an inorganic base such aspotassium carbonate. Examples of the solvent that can be used for thereaction include 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone(DMPU), toluene, xylene, and benzene. In the Ullmann reaction, since theobjective product can be obtained in a shorter time and in a higheryield when the reaction temperature is 100° C. or higher; therefore, itis preferable to use DMPU or xylene that has a high boiling temperature.A reaction temperature of 150° C. or higher is further preferred andaccordingly DMPU is more preferably used. The reagents that can be usedfor the reaction are not limited to the above reagents.

Embodiment 3

In this embodiment, a light-emitting device including the light-emittingelement described in Embodiment 1 will be described.

In this embodiment, the light-emitting device manufactured using thelight-emitting element described in Embodiment 1 is described withreference to FIGS. 2A and 2B. Note that FIG. 2A is a top view of thelight-emitting device and FIG. 2B is a cross-sectional view taken alongthe lines A-B and C-D in FIG. 2A. This light-emitting device includes adriver circuit portion (source line driver circuit) 601, a pixel portion602, and a driver circuit portion (gate line driver circuit) 603, whichare to control the light emission of a light-emitting element andillustrated with dotted lines. Reference numeral 604 denotes a sealingsubstrate; 605, a sealing material; and 607, a space surrounded by thesealing material 605.

Reference numeral 608 denotes a wiring for transmitting signals to beinput to the source line driver circuit 601 and the gate line drivercircuit 603 and receiving signals such as a video signal, a clocksignal, a start signal, and a reset signal from a flexible printedcircuit (FPC) 609 serving as an external input terminal. Although onlythe FPC is illustrated here, a printed wiring board (PWB) may beattached to the FPC. The light-emitting device in the presentspecification includes, in its category, not only the light-emittingdevice itself but also the light-emitting device provided with the FPCor the PWB.

Next, a cross-sectional structure is described with reference to FIG.2B. The driver circuit portions and the pixel portion are formed over anelement substrate 610; FIG. 2B shows the source line driver circuit 601,which is a driver circuit portion, and one pixel in the pixel portion602.

The element substrate 610 may be a substrate containing glass, quartz,an organic resin, a metal, an alloy, or a semiconductor or a plasticsubstrate formed of fiber reinforced plastic (FRP), poly(vinyl fluoride)(PVF), polyester, or acrylic.

The structure of transistors used in pixels and driver circuits is notparticularly limited. For example, inverted staggered transistors may beused, or staggered transistors may be used. Furthermore, top-gatetransistors or bottom-gate transistors may be used. A semiconductormaterial used for the transistors is not particularly limited, and forexample, silicon, germanium, silicon carbide, gallium nitride, or thelike can be used. Alternatively, an oxide semiconductor containing atleast one of indium, gallium, and zinc, such as an In—Ga—Zn-based metaloxide, may be used.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be suppressed.

Here, an oxide semiconductor is preferably used for semiconductordevices such as the transistors provided in the pixels and drivercircuits and transistors used for touch sensors described later, and thelike. In particular, an oxide semiconductor having a wider band gap thansilicon is preferably used. When an oxide semiconductor having a widerband gap than silicon is used, the off-state current of the transistorscan be reduced.

The oxide semiconductor preferably contains at least indium (In) or zinc(Zn). Further preferably, the oxide semiconductor contains an oxiderepresented by an In-M-Zn-based oxide (M represents a metal such as Al,Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

As a semiconductor layer, it is particularly preferable to use an oxidesemiconductor film including a plurality of crystal parts whose c-axesare aligned perpendicular to a surface on which the semiconductor layeris formed or the top surface of the semiconductor layer and in which theadjacent crystal parts have no grain boundary.

The use of such materials for the semiconductor layer makes it possibleto provide a highly reliable transistor in which a change in theelectrical characteristics is suppressed.

Charge accumulated in a capacitor through a transistor including theabove-described semiconductor layer can be held for a long time becauseof the low off-state current of the transistor. When such a transistoris used in a pixel, operation of a driver circuit can be stopped while agray scale of an image displayed in each display region is maintained.As a result, an electronic device with extremely low power consumptioncan be obtained.

For stable characteristics of the transistor, a base film is preferablyprovided. The base film can be formed with a single-layer structure or astacked-layer structure using an inorganic insulating film such as asilicon oxide film, a silicon nitride film, a silicon oxynitride film,or a silicon nitride oxide film. The base film can be formed by asputtering method, a chemical vapor deposition (CVD) method (e.g., aplasma CVD method, a thermal CVD method, or a metal organic CVD (MOCVD)method), an atomic layer deposition (ALD) method, a coating method, aprinting method, or the like. Note that the base film is not necessarilyprovided.

Note that an FET 623 is illustrated as a transistor formed in the drivercircuit portion 601. In addition, the driver circuit may be formed withany of a variety of circuits such as a CMOS circuit, a PMOS circuit, oran NMOS circuit. Although a driver integrated type in which the drivercircuit is formed over the substrate is illustrated in this embodiment,the driver circuit is not necessarily formed over the substrate, and thedriver circuit can be formed outside, not over the substrate.

The pixel portion 602 includes a plurality of pixels including aswitching FET 611, a current controlling FET 612, and an anode 613electrically connected to a drain of the current controlling FET 612.One embodiment of the present invention is not limited to the structure.The pixel portion 602 may include three or more FETs and a capacitor incombination.

Note that to cover an end portion of the anode 613, an insulator 614 isformed using a positive photosensitive acrylic resin film here.

In order to improve the coverage with an EL layer or the like which isformed later, the insulator 614 is formed to have a curved surface withcurvature at its upper or lower end portion. For example, in the casewhere positive photosensitive acrylic is used as a material of theinsulator 614, only the upper end portion of the insulator 614preferably has a curved surface with a curvature radius (0.2 μm to 3μm). As the insulator 614, either a negative photosensitive resin or apositive photosensitive resin can be used.

An EL layer 616 and a cathode 617 are formed over the anode 613. Here,as a material used for the anode 613, a material having a high workfunction is preferably used. For example, a single-layer film of an ITOfilm, an indium tin oxide film containing silicon, an indium oxide filmcontaining zinc oxide at 2 wt % to 20 wt %, a titanium nitride film, achromium film, a tungsten film, a Zn film, a Pt film, or the like, astack of a titanium nitride film and a film containing aluminum as itsmain component, a stack of three layers of a titanium nitride film, afilm containing aluminum as its main component, and a titanium nitridefilm, or the like can be used. The stacked-layer structure enables lowwiring resistance and favorable ohmic contact.

The EL layer 616 is formed by any of a variety of methods such as anevaporation method using an evaporation mask, an inkjet method, and aspin coating method. The EL layer 616 has the structure described inEmbodiment 1. As another material included in the EL layer 616, a lowmolecular compound or a high molecular compound (including an oligomeror a dendrimer) may be used.

As a material used for the cathode 617, which is formed over the ELlayer 616, a material having a low work function (e.g., Al, Mg, Li, andCa, or an alloy or a compound thereof, such as MgAg, MgIn, or AlLi) ispreferably used. In the case where light generated in the EL layer 616is transmitted through the cathode 617, a stack of a thin metal film anda transparent conductive film (e.g., ITO, indium oxide containing zincoxide at 2 wt % to 20 wt %, indium tin oxide containing silicon, or zincoxide (ZnO)) is preferably used for the cathode 617.

Note that the light-emitting element is formed with the anode 613, theEL layer 616, and the cathode 617. The light-emitting element is thelight-emitting element described in Embodiment 1. In the light-emittingdevice of this embodiment, the pixel portion, which includes a pluralityof light-emitting elements, may include both the light-emitting elementdescribed in Embodiment 1 and a light-emitting element having adifferent structure.

The sealing substrate 604 is attached to the element substrate 610 withthe sealing material 605, so that a light-emitting element 618 isprovided in the space 607 surrounded by the element substrate 610, thesealing substrate 604, and the sealing material 605. The space 607 maybe filled with a filler, or may be filled with an inert gas (such asnitrogen or argon), or the sealing material. It is preferable that thesealing substrate be provided with a recessed portion and a drying agentbe provided in the recessed portion, in which case deterioration due toinfluence of moisture can be suppressed.

An epoxy-based resin or glass frit is preferably used for the sealingmaterial 605. It is preferable that such a material not be permeable tomoisture or oxygen as much as possible. As the sealing substrate 604, aglass substrate, a quartz substrate, or a plastic substrate formed offiber reinforced plastic (FRP), poly(vinyl fluoride) (PVF), polyester,or acrylic can be used.

Although not illustrated in FIGS. 2A and 2B, a protective film may beprovided over the cathode. As the protective film, an organic resin filmor an inorganic insulating film may be formed. The protective film maybe formed so as to cover an exposed portion of the sealing material 605.The protective film may be provided so as to cover surfaces and sidesurfaces of the pair of substrates and exposed side surfaces of asealing layer, an insulating layer, and the like.

The protective film can be formed using a material through which animpurity such as water does not permeate easily. Thus, diffusion of animpurity such as water from the outside into the inside can beeffectively suppressed.

As a material of the protective film, an oxide, a nitride, a fluoride, asulfide, a ternary compound, a metal, a polymer, or the like can beused. For example, the material may contain aluminum oxide, hafniumoxide, hafnium silicate, lanthanum oxide, silicon oxide, strontiumtitanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide,zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide,erbium oxide, vanadium oxide, indium oxide, aluminum nitride, hafniumnitride, silicon nitride, tantalum nitride, titanium nitride, niobiumnitride, molybdenum nitride, zirconium nitride, gallium nitride, anitride containing titanium and aluminum, an oxide containing titaniumand aluminum, an oxide containing aluminum and zinc, a sulfidecontaining manganese and zinc, a sulfide containing cerium andstrontium, an oxide containing erbium and aluminum, an oxide containingyttrium and zirconium, or the like.

The protective film is preferably formed using a deposition method withfavorable step coverage. One such method is an atomic layer deposition(ALD) method. A material that can be deposited by an ALD method ispreferably used for the protective film. A dense protective film havingreduced defects such as cracks or pinholes or a uniform thickness can beformed by an ALD method. Furthermore, damage caused to a process memberin forming the protective film can be reduced.

By an ALD method, a uniform protective film with few defects can beformed even on, for example, a surface with a complex uneven shape orupper, side, and lower surfaces of a touch panel.

As described above, the light-emitting device manufactured using thelight-emitting element described in Embodiment 1 can be obtained.

The light-emitting device in this embodiment is manufactured using thelight-emitting element described in Embodiment 1 and thus can havefavorable characteristics. Specifically, since the light-emittingelement described in Embodiment 1 has a long lifetime, thelight-emitting device can have high reliability. Since thelight-emitting device using the light-emitting element described inEmbodiment 1 has high emission efficiency, the light-emitting device canachieve low power consumption.

FIGS. 3A and 3B each illustrate an example of a light-emitting device inwhich full color display is achieved by formation of a light-emittingelement exhibiting white light emission and with the use of coloringlayers (color filters) and the like. FIG. 3A illustrates a substrate1001, a base insulating film 1002, a gate insulating film 1003, gateelectrodes 1006, 1007, and 1008, a first interlayer insulating film1020, a second interlayer insulating film 1021, a peripheral portion1042, a pixel portion 1040, a driver circuit portion 1041, anodes 1024W,1024R, 1024G, and 1024B of light-emitting elements, a partition 1025, anEL layer 1028, a cathode 1029 of the light-emitting elements, a sealingsubstrate 1031, a sealing material 1032, and the like.

In FIG. 3A, coloring layers (a red coloring layer 1034R, a greencoloring layer 1034G, and a blue coloring layer 1034B) are provided on atransparent base material 1033. A black matrix 1035 may be additionallyprovided. The transparent base material 1033 provided with the coloringlayers and the black matrix is aligned and fixed to the substrate 1001.Note that the coloring layers and the black matrix 1035 are covered withan overcoat layer 1036. In FIG. 3A, light emitted from part of thelight-emitting layer does not pass through the coloring layers, whilelight emitted from the other part of the light-emitting layer passesthrough the coloring layers. The light that does not pass through thecoloring layers is white and the light that passes through any one ofthe coloring layers is red, green, or blue; thus, an image can bedisplayed using pixels of the four colors.

FIG. 3B illustrates an example in which the coloring layers (the redcoloring layer 1034R, the green coloring layer 1034G, and the bluecoloring layer 1034B) are provided between the gate insulating film 1003and the first interlayer insulating film 1020. As in the structure, thecoloring layers may be provided between the substrate 1001 and thesealing substrate 1031.

The above-described light-emitting device is a light-emitting devicehaving a structure in which light is extracted from the substrate 1001side where FETs are formed (a bottom emission structure), but may be alight-emitting device having a structure in which light is extractedfrom the sealing substrate 1031 side (a top emission structure). FIG. 4is a cross-sectional view of a light-emitting device having a topemission structure. In this case, a substrate that does not transmitlight can be used as the substrate 1001. The process up to the step offorming a connection electrode which connects the FET and the anode ofthe light-emitting element is performed in a manner similar to that ofthe light-emitting device having a bottom emission structure. Then, athird interlayer insulating film 1037 is formed to cover an electrode1022. This insulating film may have a planarization function. The thirdinterlayer insulating film 1037 can be formed using a material similarto that of the second interlayer insulating film, and can alternativelybe formed using any of other known materials.

The anodes 1024W, 1024R, 1024G, and 1024B of the light-emitting elementseach serve as an anode here, but may serve as a cathode. Furthermore, inthe case of a light-emitting device having a top emission structure asillustrated in FIG. 4, the anodes are preferably reflective electrodes.The EL layer 1028 is formed to have a structure similar to the structureof the EL layer 103, which is described in Embodiment 1, with whichwhite light emission can be obtained.

In the case of a top emission structure as illustrated in FIG. 4,sealing can be performed with the sealing substrate 1031 on which thecoloring layers (the red coloring layer 1034R, the green coloring layer1034G, and the blue coloring layer 1034B) are provided. The sealingsubstrate 1031 may be provided with the black matrix 1035 which ispositioned between pixels. The coloring layers (the red coloring layer1034R, the green coloring layer 1034G, and the blue coloring layer1034B) and the black matrix may be covered with the overcoat layer 1036.Note that a light-transmitting substrate is used as the sealingsubstrate 1031. Although an example in which full color display isperformed using four colors of red, green, blue, and white is shownhere, there is no particular limitation and full color display usingfour colors of red, yellow, green, and blue or three colors of red,green, and blue may be performed.

In the light-emitting device having a top emission structure, amicrocavity structure can be favorably employed. A light-emittingelement with a microcavity structure is formed with the use of areflective electrode as the anode and a semi-transmissive andsemi-reflective electrode as the cathode. The light-emitting elementwith a microcavity structure includes at least an EL layer between thereflective electrode and the semi-transmissive and semi-reflectiveelectrode, which includes at least a light-emitting layer serving as alight-emitting region.

Note that the reflective electrode has a visible light reflectivity of40% to 100%, preferably 70% to 100%, and a resistivity of 1×10⁻² Ωcm orlower. In addition, the semi-transmissive and semi-reflective electrodehas a visible light reflectivity of 20% to 80%, preferably 40% to 70%,and a resistivity of 1×10⁻² Ωcm or lower.

Light emitted from the light-emitting layer included in the EL layer isreflected and resonated by the reflective electrode and thesemi-transmissive and semi-reflective electrode.

In the light-emitting element, by changing thicknesses of thetransparent conductive film, the composite material, thecarrier-transport material, and the like, the optical path lengthbetween the reflective electrode and the semi-transmissive andsemi-reflective electrode can be changed. Thus, light with a wavelengththat is resonated between the reflective electrode and thesemi-transmissive and semi-reflective electrode can be intensified whilelight with a wavelength that is not resonated therebetween can beattenuated.

Note that light that is reflected back by the reflective electrode(first reflected light) considerably interferes with light that directlyenters the semi-transmissive and semi-reflective electrode from thelight-emitting layer (first incident light). For this reason, theoptical path length between the reflective electrode and thelight-emitting layer is preferably adjusted to (2n−1)λ/4 (n is a naturalnumber of 1 or larger and λ is a wavelength of color to be amplified).By adjusting the optical path length, the phases of the first reflectedlight and the first incident light can be aligned with each other andthe light emitted from the light-emitting layer can be furtheramplified.

Note that in the above structure, the EL layer may include a pluralityof light-emitting layers or may include a single light-emitting layer.The tandem light-emitting element described above may be combined with aplurality of EL layers; for example, a light-emitting element may have astructure in which a plurality of EL layers are provided, acharge-generation layer is provided between the EL layers, and each ELlayer includes a plurality of light-emitting layers or a singlelight-emitting layer.

With the microcavity structure, emission intensity with a specificwavelength in the front direction can be increased, whereby powerconsumption can be reduced. Note that in the case of a light-emittingdevice which displays images with subpixels of four colors, red, yellow,green, and blue, the light-emitting device can have favorablecharacteristics because the luminance can be increased owing to yellowlight emission and each subpixel can employ a microcavity structuresuitable for wavelengths of the corresponding color.

The light-emitting device in this embodiment is manufactured using thelight-emitting element described in Embodiment 1 and thus can havefavorable characteristics. Specifically, since the light-emittingelement described in Embodiment 1 has a long lifetime, thelight-emitting device can have high reliability. Since thelight-emitting device using the light-emitting element described inEmbodiment 1 has high emission efficiency, the light-emitting device canachieve low power consumption.

The active matrix light-emitting device is described above, whereas apassive matrix light-emitting device is described below. FIGS. 5A and 5Billustrate a passive matrix light-emitting device manufactured using thepresent invention. Note that FIG. 5A is a perspective view of thelight-emitting device, and FIG. 5B is a cross-sectional view taken alongthe line X-Y in FIG. 5A. In FIGS. 5A and 5B, over a substrate 951, an ELlayer 955 is provided between an electrode 952 and an electrode 956. Anend portion of the electrode 952 is covered with an insulating layer953. A partition layer 954 is provided over the insulating layer 953.The sidewalls of the partition layer 954 are aslope such that thedistance between both sidewalls is gradually narrowed toward the surfaceof the substrate. In other words, a cross section taken along thedirection of the short side of the partition layer 954 is trapezoidal,and the lower side (a side of the trapezoid that is parallel to thesurface of the insulating layer 953 and is in contact with theinsulating layer 953) is shorter than the upper side (a side of thetrapezoid that is parallel to the surface of the insulating layer 953and is not in contact with the insulating layer 953). The partitionlayer 954 thus provided can prevent defects in the light-emittingelement due to static electricity or others. The passive-matrixlight-emitting device also includes the light-emitting element describedin Embodiment 1; thus, the light-emitting device can have highreliability or low power consumption.

Since many minute light-emitting elements arranged in a matrix in thelight-emitting device described above can each be controlled, thelight-emitting device can be suitably used as a display device fordisplaying images.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 4

In this embodiment, an example in which the light-emitting elementdescribed in Embodiment 1 is used for a lighting device will bedescribed with reference to FIGS. 6A and 6B. FIG. 6B is a top view ofthe lighting device, and FIG. 6A is a cross-sectional view taken alongthe line e-f in FIG. 6B.

In the lighting device in this embodiment, an anode 401 is formed over asubstrate 400 which is a support and has a light-transmitting property.The anode 401 corresponds to the anode 101 in Embodiment 1. When lightis extracted through the anode 401 side, the anode 401 is formed using amaterial having a light-transmitting property.

A pad 412 for applying voltage to a cathode 404 is provided over thesubstrate 400.

An EL layer 403 is formed over the anode 401. The structure of the ELlayer 403 corresponds to, for example, the structure of the EL layer 103in Embodiment 1, or the structure in which the light-emitting units 511and 512 and the charge-generation layer 513 are combined. Refer to thedescriptions for the structure.

The cathode 404 is formed to cover the EL layer 403. The cathode 404corresponds to the cathode 102 in Embodiment 1. The cathode 404 isformed using a material having high reflectance when light is extractedthrough the anode 401 side. The cathode 404 is connected to the pad 412,whereby voltage is applied.

As described above, the lighting device described in this embodimentincludes a light-emitting element including the anode 401, the EL layer403, and the cathode 404. Since the light-emitting element is alight-emitting element with high emission efficiency, the lightingdevice in this embodiment can be a lighting device having low powerconsumption.

The substrate 400 provided with the light-emitting element having theabove structure is fixed to a sealing substrate 407 with sealingmaterials 405 and 406 and sealing is performed, whereby the lightingdevice is completed. It is possible to use only either the sealingmaterial 405 or the sealing material 406. The inner sealing material 406(not shown in FIG. 6B) can be mixed with a desiccant which enablesmoisture to be adsorbed, increasing reliability.

When parts of the pad 412 and the anode 401 are extended to the outsideof the sealing materials 405 and 406, the extended parts can serve asexternal input terminals. An IC chip 420 mounted with a converter or thelike may be provided over the external input terminals.

The lighting device described in this embodiment includes as an ELelement the light-emitting element described in Embodiment 1; thus, thelight-emitting device can have high reliability. In addition, thelight-emitting device can consume less power.

Embodiment 5

In this embodiment, examples of electronic devices each including thelight-emitting element described in Embodiment 1 are described. Thelight-emitting element described in Embodiment 1 has a long lifetime andhigh reliability. As a result, the electronic devices described in thisembodiment can each include a light-emitting portion having highreliability.

Examples of the electronic devices to which the above light-emittingelement is applied include television devices (also referred to as TV ortelevision receivers), monitors for computers and the like, cameras suchas digital cameras and digital video cameras, digital photo frames,mobile phones (also referred to as cell phones or mobile phone devices),portable game machines, portable information terminals, audio playbackdevices, large game machines such as pachinko machines, and the like.Specific examples of these electronic devices are given below.

FIG. 7A illustrates an example of a television device. In the televisiondevice, a display portion 7103 is incorporated in a housing 7101. Here,the housing 7101 is supported by a stand 7105. Images can be displayedon the display portion 7103, and in the display portion 7103, thelight-emitting elements described in Embodiment 1 are arranged in amatrix.

Operation of the television device can be performed with an operationswitch of the housing 7101 or a separate remote controller 7110. Withoperation keys 7109 of the remote controller 7110, channels and volumecan be controlled and images displayed on the display portion 7103 canbe controlled. The remote controller 7110 may be provided with a displayportion 7107 for displaying data output from the remote controller 7110.

Note that the television device is provided with a receiver, a modem,and the like. With the use of the receiver, general televisionbroadcasting can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 7B1 illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnection port 7205, a pointing device 7206, and the like. Note thatthis computer is manufactured by arranging light-emitting elementsdescribed in Embodiment 1 in a matrix in the display portion 7203. Thecomputer illustrated in FIG. 7B1 may have a structure illustrated inFIG. 7B2. The computer illustrated in FIG. 7B2 is provided with a seconddisplay portion 7210 instead of the keyboard 7204 and the pointingdevice 7206. The second display portion 7210 has a touch screen, andinput can be performed by operation of images, which are displayed onthe second display portion 7210, with a finger or a dedicated pen. Thesecond display portion 7210 can also display images other than thedisplay for input. The display portion 7203 may also have a touchscreen. Connecting the two screens with a hinge can prevent troubles;for example, the screens can be prevented from being cracked or brokenwhile the computer is being stored or carried.

FIG. 7C illustrates a portable game machine having two housings, ahousing 7301 and a housing 7302, which are connected with a jointportion 7303 so that the portable game machine can be opened or folded.The housing 7301 incorporates a display portion 7304 in which thelight-emitting elements described in Embodiment 1 are arranged in amatrix, and the housing 7302 incorporates a display portion 7305. Inaddition, the portable game machine illustrated in FIG. 7C includes aspeaker portion 7306, a recording medium insertion portion 7307, an LEDlamp 7308, input means (an operation key 7309, a connection terminal7310, a sensor 7311 (a sensor having a function of measuring or sensingforce, displacement, position, speed, acceleration, angular velocity,rotational frequency, distance, light, liquid, magnetism, temperature,chemical substance, sound, time, hardness, electric field, current,voltage, electric power, radiation, flow rate, humidity, gradient,oscillation, odor, or infrared rays), and a microphone 7312), and thelike. Needless to say, the structure of the portable game machine is notlimited to the above as long as the display portion in which thelight-emitting elements described in Embodiment 1 are arranged in amatrix is used as either the display portion 7304 or the display portion7305, or both, and the structure can include other accessories asappropriate. The portable game machine illustrated in FIG. 7C has afunction of reading out a program or data stored in a recoding medium todisplay it on the display portion, and a function of sharing informationwith another portable game machine by wireless communication. Note thatfunctions of the portable game machine illustrated in FIG. 7C are notlimited to them, and the portable game machine can have variousfunctions.

FIG. 7D illustrates an example of a portable terminal. A mobile phone7400 is provided with a display portion 7402 incorporated in a housing7401, operation buttons 7403, an external connection port 7404, aspeaker 7405, a microphone 7406, and the like. Note that the mobilephone 7400 has the display portion 7402 in which the light-emittingelements described in Embodiment 1 are arranged in a matrix.

When the display portion 7402 of the portable terminal illustrated inFIG. 7D is touched with a finger or the like, data can be input into theportable terminal. In this case, operations such as making a call andcreating an e-mail can be performed by touching the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting information such ascharacters. The third mode is a display-and-input mode in which twomodes of the display mode and the input mode are combined.

For example, in the case of making a call or creating an e-mail, acharacter input mode is selected for the display portion 7402 so thatcharacters displayed on a screen can be input. In this case, it ispreferable to display a keyboard or number buttons on almost the entirescreen of the display portion 7402.

When a sensing device including a sensor such as a gyroscope or anacceleration sensor for detecting inclination is provided inside theportable terminal, display on the screen of the display portion 7402 canbe automatically changed in direction by determining the orientation ofthe portable terminal (whether the portable terminal is placedhorizontally or vertically).

The screen modes are switched by touch on the display portion 7402 oroperation with the operation buttons 7403 of the housing 7401. Thescreen modes can be switched depending on the kind of images displayedon the display portion 7402. For example, when a signal of an imagedisplayed on the display portion is a signal of moving image data, thescreen mode is switched to the display mode. When the signal is a signalof text data, the screen mode is switched to the input mode.

Moreover, in the input mode, if a signal detected by an optical sensorin the display portion 7402 is detected and the input by touch on thedisplay portion 7402 is not performed for a certain period, the screenmode may be controlled so as to be changed from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by thedisplay portion 7402 while in touch with the palm or the finger, wherebypersonal authentication can be performed. Furthermore, by providing abacklight or a sensing light source which emits near-infrared light inthe display portion, an image of a finger vein, or a palm vein can betaken.

Note that the structure shown in this embodiment can be combined withany of the structures in Embodiments 1 to 4 as appropriate.

As described above, the application range of the light-emitting deviceincluding the light-emitting element described in Embodiment 1 is wideso that this light-emitting device can be applied to electronic devicesin a variety of fields. By using the light-emitting element described inEmbodiment 1, an electronic device having high reliability can beobtained.

FIG. 8 illustrates an example of a liquid crystal display device usingthe light-emitting element described in Embodiment 1 for a backlight.The liquid crystal display device illustrated in FIG. 8 includes ahousing 901, a liquid crystal layer 902, a backlight unit 903, and ahousing 904. The liquid crystal layer 902 is connected to a driver IC905. The light-emitting element described in Embodiment 1 is used forthe backlight unit 903, to which current is supplied through a terminal906.

The light-emitting element described in Embodiment 1 is used for thebacklight of the liquid crystal display device; thus, the backlight canhave reduced power consumption. In addition, the use of thelight-emitting element described in Embodiment 1 enables manufacture ofa planar-emission lighting device and further a larger-areaplanar-emission lighting device; therefore, the backlight can be alarger-area backlight, and the liquid crystal display device can also bea larger-area device. Furthermore, the light-emitting device includingthe light-emitting element described in Embodiment 1 can be thinner thana conventional one; accordingly, the display device can also be thinner.

FIG. 9 illustrates an example in which the light-emitting elementdescribed in Embodiment 1 is used for a table lamp which is a lightingdevice. The table lamp illustrated in FIG. 9 includes a housing 2001 anda light source 2002, and the lighting device described in Embodiment 4may be used for the light source 2002.

FIG. 10 illustrates an example in which the light-emitting elementdescribed in Embodiment 1 is used for an indoor lighting device 3001.Since the light-emitting element described in Embodiment 1 has highreliability, the lighting device can have high reliability. Furthermore,since the light-emitting element described in Embodiment 1 can have alarge area, the light-emitting element can be used for a large-arealighting device. Furthermore, since the light-emitting element describedin Embodiment 1 is thin, the light-emitting element can be used for alighting device having a reduced thickness.

The light-emitting element described in Embodiment 1 can also be usedfor an automobile windshield or an automobile dashboard. FIG. 11illustrates one mode in which the light-emitting element described inEmbodiment 1 is used for an automobile windshield and an automobiledashboard. Display regions 5000 to 5005 each include the light-emittingelement described in Embodiment 1.

The display region 5000 and the display region 5001 are display devicesprovided in the automobile windshield in which the light-emittingelements described in Embodiment 1 are incorporated. The light-emittingelements described in Embodiment 1 can be formed into what is called asee-through display device, through which the opposite side can be seen,by including an anode and a cathode formed of electrodes having alight-transmitting property. Such see-through display devices can beprovided even in the automobile windshield, without hindering thevision. Note that in the case where a driving transistor or the like isprovided, a transistor having a light-transmitting property, such as anorganic transistor using an organic semiconductor material or atransistor using an oxide semiconductor, is preferably used.

The display region 5002 is a display device provided in a pillar portionin which the light-emitting element described in Embodiment 1 isincorporated. The display region 5002 can compensate for the viewhindered by the pillar by showing an image taken by an imaging unitprovided in the car body. Similarly, the display region 5003 provided inthe dashboard can compensate for the view hindered by the car body byshowing an image taken by an imaging unit provided in the outside of thecar body, which leads to elimination of blind areas and enhancement ofsafety. Showing an image so as to compensate for the area which a drivercannot see makes it possible for the driver to confirm safety easily andcomfortably.

The display region 5004 and the display region 5005 can provide avariety of kinds of information such as navigation data, a speedometer,a tachometer, a mileage, a fuel level, a gearshift state, andair-condition setting. The content or layout of the display can befreely changed by a user as appropriate. Note that such information canalso be shown by the display regions 5000 to 5003. The display regions5000 to 5005 can also be used as lighting devices.

FIGS. 12A and 12B illustrate an example of a foldable tablet terminal.FIG. 12A illustrates the tablet terminal which is unfolded. The tabletterminal includes a housing 9630, a display portion 9631 a, a displayportion 9631 b, a display mode switch 9034, a power switch 9035, apower-saving mode switch 9036, a clasp 9033, and an operation switch9038. Note that in the tablet terminal, one or both of the displayportion 9631 a and the display portion 9631 b is/are formed using alight-emitting device which includes the light-emitting elementdescribed in Embodiment 1.

Part of the display portion 9631 a can be a touchscreen region 9632 aand data can be input when a displayed operation key 9637 is touched.Although half of the display portion 9631 a has only a display functionand the other half has a touchscreen function, one embodiment of thepresent invention is not limited to the structure. The whole displayportion 9631 a may have a touchscreen function. For example, a keyboardcan be displayed on the entire region of the display portion 9631 a sothat the display portion 9631 a is used as a touchscreen, and thedisplay portion 9631 b can be used as a display screen.

Like the display portion 9631 a, part of the display portion 9631 b canbe a touchscreen region 9632 b. When a switching button 9639 forshowing/hiding a keyboard on the touchscreen is touched with a finger, astylus, or the like, the keyboard can be displayed on the displayportion 9631 b.

Touch input can be performed in the touchscreen region 9632 a and thetouchscreen region 9632 b at the same time.

The display mode switch 9034 can switch the display between portraitmode, landscape mode, and the like, and between monochrome display andcolor display, for example. The power-saving mode switch 9036 cancontrol display luminance in accordance with the amount of externallight in use of the tablet terminal sensed by an optical sensorincorporated in the tablet terminal. Another sensing device including asensor such as a gyroscope or an acceleration sensor for sensinginclination may be incorporated in the tablet terminal, in addition tothe optical sensor.

Although FIG. 12A illustrates an example in which the display portion9631 a and the display portion 9631 b have the same display area, oneembodiment of the present invention is not limited to the example. Thedisplay portion 9631 a and the display portion 9631 b may have differentdisplay areas and different display quality. For example, higherdefinition images may be displayed on one of the display portions 9631 aand 9631 b.

FIG. 12B illustrates the tablet terminal which is folded. The tabletterminal in this embodiment includes the housing 9630, a solar cell9633, a charge and discharge control circuit 9634, a battery 9635, and aDCDC converter 9636. In FIG. 12B, a structure including the battery 9635and the DCDC converter 9636 is illustrated as an example of the chargeand discharge control circuit 9634.

Since the tablet terminal is foldable, the housing 9630 can be closedwhen the tablet terminal is not in use. As a result, the display portion9631 a and the display portion 9631 b can be protected, therebyproviding a tablet terminal with high endurance and high reliability forlong-term use.

The tablet terminal illustrated in FIGS. 12A and 12B can have otherfunctions such as a function of displaying various kinds of data (e.g.,a still image, a moving image, and a text image), a function ofdisplaying a calendar, a date, the time, or the like on the displayportion, a touch-input function of operating or editing the datadisplayed on the display portion by touch input, and a function ofcontrolling processing by various kinds of software (programs).

The solar cell 9633 provided on a surface of the tablet terminal cansupply power to the touchscreen, the display portion, a video signalprocessing portion, or the like. Note that a structure in which thesolar cell 9633 is provided on one or both surfaces of the housing 9630is preferable because the battery 9635 can be charged efficiently.

The structure and operation of the charge and discharge control circuit9634 illustrated in FIG. 12B will be described with reference to a blockdiagram of FIG. 12C. FIG. 12C illustrates the solar cell 9633, thebattery 9635, the DCDC converter 9636, a converter 9638, switches SW1 toSW3, and a display portion 9631. The battery 9635, the DCDC converter9636, the converter 9638, and the switches SW1 to SW3 correspond to thecharge and discharge control circuit 9634 illustrated in FIG. 12B.

First, description is made on an example of the operation in the casewhere power is generated by the solar cell 9633 with the use of externallight. The voltage of the power generated by the solar cell is raised orlowered by the DCDC converter 9636 so as to be voltage for charging thebattery 9635. Then, when power from the solar cell 9633 is used for theoperation of the display portion 9631, the switch SW1 is turned on andthe voltage of the power is raised or lowered by the converter 9638 soas to be voltage needed for the display portion 9631. When images arenot displayed on the display portion 9631, the switch SW1 is turned offand the switch SW2 is turned on so that the battery 9635 is charged.

Although the solar cell 9633 is described as an example of a powergeneration means, the power generation means is not particularlylimited, and the battery 9635 may be charged by another power generationmeans such as a piezoelectric element or a thermoelectric conversionelement (Peltier element). The battery 9635 may be charged by anon-contact power transmission module capable of performing charging bytransmitting and receiving power wirelessly (without contact), or any ofthe other charge means used in combination, and the power generationmeans is not necessarily provided.

One embodiment of the present invention is not limited to the tabletterminal having the shape illustrated in FIGS. 12A to 12C as long as thedisplay portion 9631 is included.

FIGS. 13A to 13C illustrate a foldable portable information terminal9310. FIG. 13A illustrates the portable information terminal 9310 thatis opened. FIG. 13B illustrates the portable information terminal 9310that is being opened or being folded. FIG. 13C illustrates the portableinformation terminal 9310 that is folded. The portable informationterminal 9310 is highly portable when folded. When the portableinformation terminal 9310 is opened, a seamless large display region ishighly browsable.

A display panel 9311 is supported by three housings 9315 joined togetherby hinges 9313. The display panel 9311 may be a touch panel (aninput/output device) including a touch sensor (an input device). Bybending the display panel 9311 at a connection portion between twohousings 9315 with the use of the hinges 9313, the portable informationterminal 9310 can be reversibly changed in shape from an opened state toa folded state. The light-emitting device of one embodiment of thepresent invention can be used for the display panel 9311. A displayregion 9312 in the display panel 9311 includes a display region that ispositioned at a side surface of the portable information terminal 9310that is folded. On the display region 9312, information icons,frequently-used applications, file shortcuts to programs, and the likecan be displayed, and confirmation of information and start ofapplication can be smoothly performed.

Note that an organic compound having a substituted or unsubstitutedbenzonaphthofuran skeleton and one substituted or unsubstituted amineskeleton, which is one embodiment of the present invention, can be usedfor an organic thin film solar cell. More specifically, the compound hasa carrier-transport property and therefore can be used in acarrier-transport layer or a carrier-injection layer. In addition, afilm of a mixture of the compound and an acceptor substance can be usedas a charge-generation layer. Furthermore, the compound can bephotoexcited and hence can be used for a power generation layer.

Example 1 Synthesis Example 1

This synthesis example specifically shows an example of synthesizingN-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BnfABP), which is the organic compound of one embodimentof the present invention represented by Structural Formula (142) inEmbodiment. The structural formula of BnfABP is as follows.

Step 1: Synthesis of 6-iodobenzo[b]naphtho[1,2-d]furan

Into a 500 mL three-neck flask was put 8.5 g (39 mmol) ofbenzo[b]naphtho[1,2-d]furan, and the air in the flask was replaced withnitrogen. Then, 195 mL of tetrahydrofuran (THF) was added thereto. Afterthis solution was cooled to −75° C., 25 mL (40 mmol) of n-butyllithium(a 1.59 mol/L n-hexane solution) was dropped into this solution. Afterthe dropping, the resulting solution was stirred at room temperature for1 hour. After a predetermined period of time, the resulting solution wascooled to −75° C. Then, a solution in which 10 g (40 mmol) of iodine hadbeen dissolved in 40 mL of THF was dropped into this solution. After thedropping, the resulting solution was stirred for 17 hours while thetemperature of the solution was returned to room temperature. Next, anaqueous solution of sodium thiosulfate was added to the mixture, and theresulting mixture was stirred for 1 hour. Then, the organic layer of themixture was washed with water and dried with magnesium sulfate. Afterthe drying, the mixture was gravity-filtered to give a solution. Theresulting solution was suction-filtered through Florisil (Catalog No.066-05265 produced by Wako Pure Chemical Industries, Ltd.) and Celite(Catalog No. 537-02305 produced by Wako Pure Chemical Industries, Ltd.)to give a filtrate. The resulting filtrate was concentrated to give asolid. The resulting solid was recrystallized from toluene to give 6.0 g(18 mmol) of the target white powder in a yield of 45%. A synthesisscheme (a-1) of Step 1 is shown below.

Step 2: Synthesis of 6-phenylbenzo[b]naphtho[1,2-d]furan

Into a 200 mL three-neck flask were put 6.0 g (18 mmol) of6-iodobenzo[b]naphtho[1,2-d]furan, 2.4 g (19 mmol) of phenylboronicacid, 70 mL of toluene, 20 mL of ethanol, and 22 mL of an aqueoussolution of potassium carbonate (2.0 mol/L). This mixture was degassedby being stirred while the pressure was reduced. After the degassing,the air in the flask was replaced with nitrogen, and then 480 mg (0.42mmol) of tetrakis(triphenylphosphine)palladium(0) was added to themixture. The resulting mixture was stirred at 90° C. under a nitrogenstream for 12 hours. After a predetermined period of time, water wasadded to the mixture, and an aqueous layer was subjected to extractionwith toluene. The extracted solution and an organic layer were combined,and the mixture was washed with water and then dried with magnesiumsulfate. The mixture was gravity-filtered to give a filtrate. Theresulting filtrate was concentrated to give a solid, and the resultingsolid was dissolved in toluene. The resulting solution wassuction-filtered through Celite (Catalog No. 531-16855 produced by WakoPure Chemical Industries, Ltd.), Florisil (Catalog No. 540-00135produced by Wako Pure Chemical Industries, Ltd.), and alumina to give afiltrate. The resulting filtrate was concentrated to give a solid. Theresulting solid was recrystallized from toluene to give 4.9 g (17 mmol)of the target white solid in a yield of 93%. A synthesis scheme (b-1) ofStep 2 is shown below.

Step 3: Synthesis of 8-iodo-6-phenylbenzo[b]naphtho[1,2,d]furan

Into a 300 mL three-neck flask was put 4.9 g (17 mmol) of6-phenylbenzo[b]naphtho[1,2-d]furan, and the air in the flask wasreplaced with nitrogen. Then, 87 mL of tetrahydrofuran (THF) was addedthereto. The resulting solution was cooled to −75° C. Then, 11 mL (18mmol) of n-butyllithium (a 1.59 mol/L n-hexane solution) was droppedinto the solution. After the dropping, the resulting solution wasstirred at room temperature for 1 hour. After a predetermined period oftime, the resulting solution was cooled to −75° C. Then, a solution inwhich 4.6 g (18 mmol) of iodine had been dissolved in 18 mL of THF wasdropped into the resulting solution. The resulting solution was stirredfor 17 hours while the temperature of the solution was returned to roomtemperature. After the stirring, an aqueous solution of sodiumthiosulfate was added to the mixture, and the resulting mixture wasstirred for one hour. Then, an organic layer of the mixture was washedwith water and dried with magnesium sulfate. The mixture wasgravity-filtered to give a filtrate. The resulting filtrate wassuction-filtered through Celite (Catalog No. 531-16855 produced by WakoPure Chemical Industries, Ltd.), Florisil (Catalog No. 540-00135produced by Wako Pure Chemical Industries, Ltd.), and alumina to give afiltrate. The resulting filtrate was concentrated to give a solid. Theresulting solid was recrystallized from toluene to give 3.7 g (8.8 mmol)of the target white solid in a yield of 53%. A synthesis scheme (c-1) ofStep 3 is shown below.

Step 4: Synthesis of 6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine

Into a 200 mL three-neck flask were added 5.0 g (12 mmol) of8-iodo-6-phenylbenzo[b]naphtho[1,2-d]furan synthesized in Step 3 and 2.9g (30 mmol) of sodium tert-butoxide. The air in the flask was replacedwith nitrogen. After that, 60 mL of toluene and 1.4 g (13 mmol) ofaniline, and 0.4 mL of tri(tert-butyl)phosphine (10 wt % hexanesolution) were added. After this mixture was degassed under reducedpressure, the temperature was set at 60° C. under a nitrogen stream, 60mg (0.1 mmol) of bis(dibenzylideneacetone)palladium(0) was added, andthis mixture was stirred at 60° C. for 40 minutes. After the stirring,the obtained mixture was washed with water and a saturated aqueoussolution of sodium chloride, and the organic layer was dried withmagnesium sulfate. After the magnesium sulfate was removed by gravityfiltration, the obtained filtrate was concentrated to give a whitesolid. This solid was purified by silica gel column chromatography (adeveloping solvent was a mixed solvent of toluene:hexane=1:2) to give3.5 g of the target white solid in a yield of 77%. A synthesis scheme(d-1) of Step 4 is shown below.

¹H NMR data of the obtained white solid are shown below.

¹H NMR (chloroform-d, 500 MHz): δ=6.23 (s, 1H), 7.04 (t, J=7.5 Hz, 1H),7.24-7.26 (m, 2H), 7.34-7.41 (m, 4H), 7.47 (t, J=8.0 Hz, 1H), 7.54-7.60(m, 3H), 7.74 (t, J=7.5 Hz, 1H), 7.95 (d, J=6.5 Hz, 2H), 7.99 (dd,J1=1.5 Hz, J2=7.0 Hz, 1H), 8.03 (s, 1H), 8.08 (d, J=8.0 Hz, 1H), 8.66(d, J=9.0 Hz, 1H).

Step 5: Synthesis ofN-4-biphenyl-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine

Into a 200 mL three-neck flask were put 1.3 g (5.0 mmol) of4-bromobiphenyl, 1.9 g (5.0 mmol) of6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine synthesized in Step 4,0.14 g (0.30 mmol) of2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (abbreviation:X-Phos), and 1.5 g (15 mmol) of sodium tert-butoxide. The air in theflask was replaced with nitrogen, and then 25 mL of toluene was added.After this mixture was degassed under reduced pressure, the temperaturewas set at 60° C. under a nitrogen stream, 61 mg (0.10 mmol) ofbis(dibenzylideneacetone)palladium(0) was added, and this mixture wasstirred at 80° C. for 3 hours. After the stirring, the obtained mixturewas washed with water and a saturated aqueous solution of sodiumchloride, and the organic layer was dried with magnesium sulfate. Afterthe magnesium sulfate was removed by gravity filtration, the obtainedfiltrate was concentrated to give a brown solid. This solid was purifiedby silica gel column chromatography (a developing solvent was a mixedsolvent of toluene:hexane=3:7) to give 2.0 g of the target pale yellowsolid in a yield of 67%. A synthesis scheme (e-1) of Step 5 is shownbelow.

¹H NMR data of the obtained pale yellow solid are shown below. FIGS. 14Aand 14B are ¹H NMR charts. Note that FIG. 14B is a chart showing anenlarged part of FIG. 14A in the range of 7.00 ppm to 9.00 ppm. Theseresults indicate that BnfABP, which is the organic compound of oneembodiment of the present invention, was obtained.

¹H NMR (dichloromethane-d2, 500 MHz): δ=7.11 (t, J=7.0 Hz, 1H), 7.16 (t,J=7.0 Hz, 4H), 7.22-7.33 (m, 7H), 7.39-7.47 (m, 5H), 7.53-7.60 (m, 5H),7.74 (t, J=7.0 Hz, 1H), 8.02 (s, 1H), 8.06 (d, J=8.0 Hz, 1H), 8.23 (d,J=8.0 Hz, 1H), 8.66 (d, J=8.0 Hz, 1H).

By train sublimation, 1.5 g of the obtained pale yellow solid waspurified. The purification by sublimation was carried out under apressure of 3.6 Pa, with a flow rate of argon gas of 15 mL/min, at atemperature of 235° C. to 250° C., and for 16 hours. After thepurification by sublimation, 1.4 g of the target pale yellow solid wasobtained at a collection rate of 90%.

Next, the ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as “absorption spectrum”) and emission spectrum of a toluenesolution and a solid thin film of BnfABP were measured. The solid thinfilm was formed over a quartz substrate by a vacuum evaporation method.The absorption spectrum of the toluene solution was measured using anultraviolet-visible light spectrophotometer (V550 type manufactured byJASCO Corporation), the spectrum of toluene only put in a quartz cellwas subtracted from the measured spectrum. The absorption spectrum ofthe thin film was measured using a spectrophotometer (U-4100Spectrophotometer, manufactured by Hitachi High-TechnologiesCorporation). The emission spectra were measured using a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.).FIG. 15 shows the measurement results of the absorption and emissionspectra of the obtained toluene solution and FIG. 16 shows themeasurement results of the absorption and emission spectra of theobtained thin film.

From FIG. 15, the toluene solution of BnfABP has absorption peaks ataround 376 nm, 340 nm, and 321 nm, and an emission peak at 417 nm(excitation wavelength: 370 nm).

From FIG. 16, the thin film of BnfABP has absorption peaks at around 387nm, 346 nm, 326 nm, 294 nm, and 262 nm, and an emission peak at 440 nm(excitation wavelength: 360 nm).

The HOMO level and the LUMO level of BnfABP were obtained through acyclic voltammetry (CV) measurement. A calculation method is describedbelow.

An electrochemical analyzer (ALS model 600A or 600C, manufactured by BASInc.) was used as a measurement apparatus. As for a solution used forthe CV measurement, dehydrated dimethylformamide (DMF, product ofSigma-Aldrich Inc., 99.8%, catalog No. 22705-6) was used as a solvent,and tetra-n-butylammonium perchlorate (n-Bu₄NClO₄, product of TokyoChemical Industry Co., Ltd., catalog No. T0836), which was a supportingelectrolyte, was dissolved in the solvent such that the concentration oftetra-n-butylammonium perchlorate was 100 mmol/L. Further, the object tobe measured was also dissolved in the solvent such that theconcentration thereof was 2 mmol/L. A platinum electrode (PTE platinumelectrode, manufactured by BAS Inc.) was used as a working electrode,another platinum electrode (Pt counter electrode for VC-3 (5 cm),manufactured by BAS Inc.) was used as an auxiliary electrode, and anAg/Ag⁺ electrode (RE7 reference electrode for nonaqueous solvent,manufactured by BAS Inc.) was used as a reference electrode. Note thatthe measurement was performed at room temperature (20° C. to 25° C.). Inaddition, the scan speed at the CV measurement was set to 0.1 V/sec, andan oxidation potential Ea [V] and a reduction potential Ec [V] withrespect to the reference electrode were measured. The potential Ea is anintermediate potential of an oxidation-reduction wave, and Ec is anintermediate potential of a reduction-oxidation wave. Here, thepotential energy of the reference electrode used in this example withrespect to the vacuum level is found to be −4.94 [eV], and thus, theHOMO level and the LUMO level can be obtained from the followingformula: HOMO level [eV]=−4.94−Ea and LUMO level [eV]=−4.94−Ec.Furthermore, the CV measurement was repeated 100 times, and theoxidation-reduction wave at the hundredth cycle and theoxidation-reduction wave at the first cycle were compared to examine theelectric stability of the compound.

As a result, it was found that the HOMO level of BnfABP was −5.59 eV andthe LUMO level thereof was −2.53 eV. After the hundredth cycle, the peakintensity of the oxidation-reduction wave maintained 83% of that of theoxidation-reduction wave at the first cycle, which indicates that BnfABPhas excellent resistant to oxidation. The thermogravimetry-differentialthermal analysis (TG/DTA) of BnfABP was performed. The measurement wasperformed using a high vacuum differential type differential thermalbalance (TG-DTA2410SA, manufactured by Bruker AXS K. K.). Themeasurement was carried out under a nitrogen stream (flow rate: 200mL/min) at normal pressure at a temperature rising rate of 10° C./min.From the relationship between weight and temperature (thermogravimetry),the 5% weight loss temperature of BnfABP was approximately 370° C. Thisindicates that BnfABP has high heat resistance. Further, differentialscanning calorimetry (DSC measurement) was performed by PyrislDSCmanufactured by PerkinElmer, Inc. In the differential scanningcalorimetry, after the temperature was raised from −10° C. to 300° C. ata temperature rising rate of 40° C./min, the temperature was held for aminute and then cooled to −10° C. at a temperature reduction rate of 40°C./min. This operation was repeated twice successively. It was foundfrom the DSC measurement that the glass transition temperature of BnfABPwas 97° C. and thus had high heat resistance.

Example 2 Synthesis Example 2

This synthesis example shows an example of synthesizingN,N-bis(biphenyl-4-yl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BBABnf), which is the organic compound of one embodimentof the present invention represented by Structural Formula (146) inEmbodiment. The structural formula of BBABnf is as follows.

Step 1: Synthesis of 6-iodobenzo[b]naphtho[1,2-d]furan

This synthesis step is similar to Step 1 in Synthesis Example 1.

Step 2: Synthesis of 6-phenylbenzo[b]naphtho[1,2-d]furan

This synthesis step is similar to Step 2 in Synthesis Example 1.

Step 3: Synthesis of 8-iodo-6-phenylbenzo[b]naphtho[1,2,d]furan

This synthesis step is similar to Step 3 in Synthesis Example 1.

Step 4: Synthesis of(9,9-dimethyl-9H-fluorene-2,7-diyl)bis(6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine

Into a 200 mL three-neck flask were put 2.1 g (5.0 mmol) of8-iodo-6-phenylbenzo[b]naphtho[1,2,-d]furan obtained in Step 3 inExample 1, 1.6 g (5.0 mmol) of di(1,1′-biphenyl-4-yl)amine, 0.17 g (0.40mmol) of 2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl(abbreviation: S-Phos), and 0.97 g (10 mmol) of sodium tert-butoxide.The air in the flask was replaced with nitrogen, and then 25 mL ofxylene was added. After this mixture was degassed under reducedpressure, the temperature was set at 80° C. under a nitrogen stream,0.12 g (0.20 mmol) of bis(dibenzylideneacetone)palladium(0) was added,and this mixture was stirred at 80° C. for 5.5 hours and further stirredat 100° C. for 5 hours. After the stirring, the obtained mixture waswashed with water and a saturated aqueous solution of sodium chloride,and the organic layer was dried with magnesium sulfate. After themagnesium sulfate was removed by gravity filtration, and the obtainedfiltrate was concentrated to give a brown solid. The obtained solid wasdissolved in toluene and filtrated through Celite (Catalog No. 537-02305produced by Wako Pure Chemical Industries, Ltd.) and alumina. Theobtained filtrate was concentrated to give 2.0 g of the target yellowsolid in a yield of 67%. A synthesis scheme (d-2) of Step 4 is shownbelow.

¹H NMR data of the obtained yellow solid are shown below. FIGS. 17A and17B are ¹H NMR charts. Note that FIG. 17B is a chart showing an enlargedpart of FIG. 17A in the range of 7.00 ppm to 9.00 ppm. These resultsindicate that BBABnf, which is the organic compound of one embodiment ofthe present invention, was obtained.

¹H NMR (dichloromethane-d2, 500 MHz): δ=7.14-7.19 (m, 3H), 7.22 (d,J=8.5 Hz, 4H), 7.29-7.33 (m, 3H), 7.41 (t, J=8.0 Hz, 4H), 7.44-7.49 (m,3H), 7.55-7.58 (m, 5H), 7.61 (d, J=8.0 Hz, 4H), 7.74 (t, J=8.0 Hz, 1H),8.02 (s, 1H), 8.06 (d, J=8.0 Hz, 1H), 8.26 (d, 1H), 8.67 (d, J=8.0 Hz,1H).

By train sublimation, 2.0 g of the obtained yellow solid was purified.The purification by sublimation was carried out under a pressure of 3.8Pa, with a flow rate of argon gas of 15 mL/min, at a temperature of 270°C., and for 16 hours. After the purification by sublimation, 1.7 g ofthe target yellow solid was obtained at a collection rate of 81%.

Next, the ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as “absorption spectrum”) and emission spectrum of a toluenesolution and a solid thin film of BBABnf were measured. The measurementwas performed with a device and a method similar to those for themeasurement of BnfABP. FIG. 18 shows the measurement results of theabsorption and emission spectra of the obtained toluene solution andFIG. 19 shows the measurement results of the absorption and emissionspectra of the obtained thin film.

From FIG. 18, the toluene solution of BBABnf has an absorption peak ataround 343 nm, and an emission peak at 420 nm (excitation wavelength:340 nm).

From FIG. 19, the thin film of BBABnf has absorption peaks at around 344nm, 325 nm, and 257 nm, and an emission peak at 439 nm (excitationwavelength: 361 nm).

The HOMO level and the LUMO level of BBABnf were obtained through acyclic voltammetry (CV) measurement. The calculation method is similarto that described in Example 1.

As a result, it was found that the HOMO level of BBABnf was −5.56 eV andthe LUMO level thereof was −2.51 eV. After the hundredth cycle, the peakintensity of the oxidation-reduction wave maintained 90% of that of theoxidation-reduction wave at the first cycle, which indicates that BBABnfhas excellent resistant to oxidation. The TG-DTA measurement and DSCmeasurement of BBABnf were performed in a manner similar to that forBnfABP. Note that in the DSC measurement, the temperature was raised to330° C. From TG-DTA measurement, the 5% weight loss temperature ofBBABnf was approximately 410° C. This indicates that BBABnf has highheat resistance. It was found from the DSC measurement that the glasstransition temperature of BBABnf was 117° C. and thus had high heatresistance.

Example 3

In this example, a light-emitting element 1 of one embodiment of thepresent invention, which is described in Embodiment 1, will bedescribed. Structural formulae of organic compounds used for thelight-emitting element 1 are shown below.

(Method for Fabricating Light-Emitting Element 1)

First, a film of indium tin oxide containing silicon oxide (ITSO) wasformed over a glass substrate by a sputtering method, so that the anode101 was formed. The thickness thereof was 70 nm and the electrode areawas 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over thesubstrate, a surface of the substrate was washed with water and baked at200° C. for 1 hour; then UV ozone treatment was performed for 370seconds.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate was cooled down for about 30 minutes.

Next, the substrate provided with the anode 101 was fixed to a substrateholder provided in the vacuum evaporation device such that the side onwhich the anode 101 was formed faced downward. Then,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN) represented by Structural Formula (i) was deposited to athickness of 5 nm over the anode 101 by an evaporation method usingresistance heating, whereby the hole-injection layer 111 was formed.

Next,N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF) represented by Structural Formula (ii) wasdeposited to a thickness of 25 nm by evaporation over the hole-injectionlayer 111, andN,N-bis(biphenyl-4-yl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BBABnf) represented by Structural Formula (iii) wasdeposited to a thickness of 5 nm by evaporation, so that thehole-transport layer 112 was formed.

After that, the light-emitting layer 113 was formed by co-evaporation of7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) represented by Structural Formula (iv) andN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn) represented by Structural Formula (v) ina weight ratio of 1:0.03 (=cgDBCzPA: 1,6mMemFLPAPrn) to a thickness of25 nm.

Then, over the light-emitting layer 113, cgDBCzPA was deposited to athickness of 10 nm by evaporation, and bathophenanthroline(abbreviation: BPhen) represented by Structural Formula (vi) wasdeposited to a thickness of 15 nm by evaporation, whereby theelectron-transport layer 114 was formed.

After the formation of the electron-transport layer 114, lithiumfluoride (LiF) was deposited to a thickness of 1 nm by evaporation toform the electron-injection layer 115. Then, aluminum was deposited to athickness of 200 nm by evaporation to form the cathode 102. Thus, thelight-emitting element 1 of this example was fabricated.

The element structure of the light-emitting element 1 is shown in thefollowing table.

TABLE 1 Hole-injection Electron-transport Electron- layer Hole-transportlayer Light-emitting layer layer injection layer 5 nm 25 nm 5 nm 25 nm10 nm 15 nm 1 nm HAT-CN PCBBiF BBABnf cgDBCzPA:1, cgDBCzPA BPhen LiF6mMemFLPAPrn (1:0.03)

The light-emitting element 1 was sealed using a glass substrate in aglove box containing a nitrogen atmosphere so as not to be exposed tothe air (specifically, a sealing material was applied to surround theelement and UV treatment and heat treatment at 80° C. for 1 hour wereperformed at the time of sealing). Then, the initial characteristics andreliability of the light-emitting element were measured. Note that themeasurements were performed at room temperature (in an atmosphere keptat 25° C.).

FIG. 20 shows the luminance-current density characteristics of thelight-emitting element 1. FIG. 21 shows the current efficiency-luminancecharacteristics of the light-emitting element 1. FIG. 22 shows theluminance-voltage characteristics of the light-emitting element 1. FIG.23 shows the current-voltage characteristics of the light-emittingelement 1. FIG. 24 shows the external quantum efficiency-luminancecharacteristics of the light-emitting element 1. FIG. 25 shows theemission spectrum of the light-emitting element 1. Table 2 shows themain characteristics of the light-emitting element 1 at around 1000cd/m².

TABLE 2 Current Current External quantum Voltage Current densityefficiency efficiency (V) (mA) (mA/cm²) Chromaticity x Chromaticity y(cd/A) (%) 2.9 0.18 5 0.14 0.16 12.4 10.8

It was found from FIGS. 20 to 25 and Table 2 that the light-emittingelement 1 of one embodiment of the present invention is a bluelight-emitting element with favorable efficiency and a low drivingvoltage.

FIG. 26 shows driving time-dependent change in luminance of thelight-emitting element under the conditions where the current value wasset to 2 mA and the current density was constant. As shown in FIG. 26,it was found that the light-emitting element is a long-lifetimelight-emitting element with a small reduction in luminance over drivingtime.

Example 4

In this example, light-emitting elements 2 and 3 of one embodiment ofthe present invention, which are described in Embodiment 1, will bedescribed. Structural formulae of organic compounds used for thelight-emitting elements 2 and 3 are shown below.

(Method for Fabricating Light-Emitting Element 2)

First, a film of indium tin oxide containing silicon oxide (ITSO) wasformed over a glass substrate by a sputtering method, so that the anode101 was formed. The thickness thereof was 70 nm and the electrode areawas 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over thesubstrate, a surface of the substrate was washed with water and baked at200° C. for 1 hour; then UV ozone treatment was performed for 370seconds.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate was cooled down for about 30 minutes.

Next, the substrate provided with the anode 101 was fixed to a substrateholder provided in the vacuum evaporation device such that the side onwhich the anode 101 was formed faced downward. Then,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN) represented by Structural Formula (i) was deposited to athickness of 5 nm over the anode 101 by an evaporation method usingresistance heating, whereby the hole-injection layer 111 was formed.

Next,N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF) represented by Structural Formula (ii) wasdeposited to a thickness of 20 nm over the hole-injection layer 111 byevaporation, whereby the first hole-transport layer 112-1 was formed;N,N-bis(biphenyl-4-yl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BBABnf) represented by Structural Formula (iii) wasdeposited to a thickness of 5 nm over the first hole-transport layer112-1 by evaporation, whereby the second hole-transport layer 112-2 wasformed; and 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole(abbreviation: PCPPn) represented by Structural Formula (vii) wasdeposited to a thickness of 5 nm over the second hole-transport layer112-2 by evaporation, whereby the third hole-transport layer 112-3 wasformed.

After that, the light-emitting layer 113 was formed by co-evaporation of7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) represented by Structural Formula (iv) andN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn) represented by Structural Formula (v) ina weight ratio of 1:0.03 (=cgDBCzPA: 1,6mMemFLPAPrn) to a thickness of25 nm.

Then, over the light-emitting layer 113, cgDBCzPA was deposited to athickness of 10 nm by evaporation, and bathophenanthroline(abbreviation: BPhen) represented by Structural Formula (vi) wasdeposited to a thickness of 15 nm by evaporation, whereby theelectron-transport layer 114 was formed.

After the formation of the electron-transport layer 114, lithiumfluoride (LiF) was deposited to a thickness of 1 nm by evaporation toform the electron-injection layer 115. Then, aluminum was deposited to athickness of 200 nm by evaporation to form the cathode 102. Thus, thelight-emitting element 2 of this example was fabricated.

(Method for Fabricating Light-Emitting Element 3)

The light-emitting element 3 was formed in the same manner as thelight-emitting element 2 except that the second hole-transport layer112-2 was formed usingN-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BnfABP) instead of BBABnf.

The element structures of the light-emitting elements 2 and 3 are shownin the following table.

TABLE 3 Hole- injection Hole-transport layer Electron-transportElectron- layer 1 2 3 Light-emitting layer layer injection layer 5 nm 20nm 5 nm 5 nm 25 nm 10 nm 15 nm 1 nm HAT-CN PCBBiF *1 PCPPn cgDBCzPA:1,cgDBCzPA BPhen LiF 6mMemFLPAPrn (1:0.03) *1 Light-emitting element 2:BBABnf, Light-emitting element 3: BnfBPA

The light-emitting elements 2 and 3 were sealed using a glass substratein a glove box containing a nitrogen atmosphere so as not to be exposedto the air (specifically, a sealing material was applied to surround theelement and UV treatment and heat treatment at 80° C. for 1 hour wereperformed at the time of sealing). Then, the initial characteristics andreliability of the light-emitting elements were measured. Note that themeasurements were performed at room temperature (in an atmosphere keptat 25° C.).

FIG. 27 shows the luminance-current density characteristics of thelight-emitting elements 2 and 3. FIG. 28 shows the currentefficiency-luminance characteristics of the light-emitting elements 2and 3. FIG. 29 shows the luminance-voltage characteristics of thelight-emitting elements 2 and 3. FIG. 30 shows the current-voltagecharacteristics of the light-emitting elements 2 and 3. FIG. 31 showsthe external quantum efficiency-luminance characteristics of thelight-emitting elements 2 and 3. FIG. 32 shows the emission spectrum ofthe light-emitting elements 2 and 3. Table 4 shows the maincharacteristics of the light-emitting elements 2 and 3 at around 1000cd/m².

TABLE 4 Current Current External quantum Voltage Current densityefficiency efficiency (V) (mA) (mA/cm²) Chromaticity x Chromaticity y(cd/A) (%) Light-emitting 3.0 0.20 5 0.14 0.16 13.8 11.8 element 2Light-emitting 3.0 0.34 9 0.14 0.15 12.8 11.5 element 3

It was found from FIGS. 27 to 32 and Table 4 that the light-emittingelements 2 and 3 of one embodiment of the present invention are bluelight-emitting elements with favorable efficiency and a low drivingvoltage.

FIG. 33 shows driving time-dependent change in luminance of thelight-emitting elements under the conditions where the current value wasset to 2 mA and the current density was constant. As shown in FIG. 33,the light-emitting elements 2 and 3 maintained 94% or more of theinitial luminance after 40-hour-driving and were found to belong-lifetime light-emitting elements with an extremely small reductionin luminance over driving time.

Example 5 Synthesis Example 3

This synthesis example shows an example of synthesizingN,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation:BBABnf(6)), which is the organic compound of one embodiment of thepresent invention represented by Structural Formula (229) in Embodiment.The structural formula of BBABnf(6) is as follows.

Step 1: Synthesis of 6-iodobenzo[b]naphtho[1,2-d]furan

The synthesis step of 6-iodobenzo[b]naphtho[1,2-d]furan is similar toStep 1 in Synthesis Example 1 in Example 1.

Step 2: Synthesis of BBABnf(6)

Into a 200 mL three-neck flask were put 2.7 g (8.0 mmol) of6-iodobenzo[b]naphtho[1,2,-d]furan obtained in Step 1, 2.6 g (8.0 mmol)of bis(1,1′-biphenyl-4-yl)amine, 0.19 g (0.40 mmol) of2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (abbreviation:X-Phos), and 1.5 g (15 mmol) of sodium tert-butoxide. The air in theflask was replaced with nitrogen, and then 40 mL of xylene was added.After this mixture was degassed under reduced pressure, the temperaturewas set at 80° C. under a nitrogen stream, 0.11 g (0.20 mmol) ofbis(dibenzylideneacetone)palladium(0) was added, and this mixture wasstirred at 120° C. for 3 hours and further stirred at 140° C. for 6.5hours. After the stirring, the obtained mixture was washed with waterand a saturated aqueous solution of sodium chloride, and the organiclayer was dried with magnesium sulfate. After the magnesium sulfate wasremoved by gravity filtration, and the obtained filtrate wasconcentrated to give a brown solid. The obtained solid was purified byhigh performance liquid chromatography (mobile phase: chloroform) togive 3.4 g of the target pale yellow solid in a yield of 79%. Asynthesis scheme (d-3) of Step 2 is shown below.

¹H NMR data of the obtained pale yellow solid are shown below. FIGS. 36Aand 36B are ¹H NMR charts. Note that FIG. 36B is a chart showing anenlarged part of FIG. 36A in the range of 7.00 ppm to 9.00 ppm. Theseresults indicate that BBABnf(6), which is the organic compound of oneembodiment of the present invention, was obtained in this synthesisexample. ¹H NMR (chloroform-d, 500 MHz): δ=7.25 (d, J=8.5 Hz, 4H), 7.31(t, J=7.5 Hz, 2H), 7.41-7.48 (m, 6H), 7.51-7.54 (m, 6H), 7.60 (d, J=8.0Hz, 4H), 7.67 (t, J=7.5 Hz, 1H), 7.73 (s, 1H), 7.88 (d, J=8.0 Hz, 1H),8.42 (d, J=7.0 Hz, 1H), 6.83 (d, J=8.0 Hz, 1H).

By train sublimation, 3.4 g of the obtained pale yellow solid waspurified. The purification by sublimation was carried out under apressure of 3.8 Pa, with a flow rate of argon gas of 15 mL/min, at atemperature of 275° C., and for 15 hours. After the purification bysublimation, 3.0 g of the target yellow solid was obtained at acollection rate of 87%.

Next, the ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as “absorption spectrum”) and emission spectrum of a toluenesolution and a solid thin film of BBABnf(6) were measured. Themeasurement was performed with a device and a method similar to thosefor the measurement in Example 1. FIG. 37 shows the measurement resultsof the absorption and emission spectra of the obtained toluene solutionand FIG. 38 shows the measurement results of the absorption and emissionspectra of the obtained thin film.

From FIG. 37, the toluene solution of BBABnf(6) has an absorption peakat around 382 nm, and an emission peak at 429 nm (excitation wavelength:337 nm).

From FIG. 38, the thin film of BBABnf(6) has an absorption peak ataround 390 nm, and an emission peak at 453 nm (excitation wavelength:390 nm).

Example 6 Synthesis Example 4

This synthesis example shows an example of synthesizingN,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation:BBABnf(8)), which is the organic compound of one embodiment of thepresent invention represented by Structural Formula (189) in Embodiment.The structural formula of BBABnf(8) is as follows.

Step 1: Synthesis of BBABnf(8)

Into a 200 mL three-neck flask were put 2.0 g (8.0 mmol) of8-chlorobenzo[b]naphtho[1,2-d]furan, 2.6 g (8.0 mmol) ofbis(1,1′-biphenyl-4-yl)amine, 0.19 g (0.40 mmol) of2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (abbreviation:X-Phos), and 1.5 g (15 mmol) of sodium tert-butoxide. The air in theflask was replaced with nitrogen, and then 40 mL of xylene was added.After this mixture was degassed under reduced pressure, the temperaturewas set at 80° C. under a nitrogen stream, 0.11 g (0.20 mmol) ofbis(dibenzylideneacetone)palladium(0) was added, and this mixture wasstirred at 120° C. for 3 hours and further stirred at 140° C. for 6.5hours. After the stirring, the obtained mixture was heated at 120° C.and filtered through Celite (Catalog No. 537-02305 produced by Wako PureChemical Industries, Ltd.), Florisil (Catalog No. 066-05265 produced byWako Pure Chemical Industries, Ltd.), and alumina without cooling. Theresulting filtrate was concentrated to give a light brown solid. Theobtained solid was purified by high performance liquid chromatography(mobile phase: chloroform) to give 2.9 g of the target pale yellow solidin a yield of 68%. A synthesis scheme (d-4) of Step 1 is shown below.

¹H NMR data of the obtained pale yellow solid are shown below. FIGS. 39Aand 39B are ¹H NMR charts. Note that FIG. 39B is a chart showing anenlarged part of FIG. 39A in the range of 7.00 ppm to 9.00 ppm. Theseresults indicate that BBABnf(8), which is the organic compound of oneembodiment of the present invention, was obtained. ¹H NMR (chloroform-d,500 MHz): δ=7.23 (d, J=8.5 Hz, 4H), 7.31 (t, J=7.5 Hz, 2H), 7.36 (d,J=8.0 Hz, 1H), 7.42 (t, J=8.0 Hz, 4H), 7.47 (d, J=8.0 Hz, 1H), 7.52 (d,J=9.0 Hz, 4H), 7.56 (t, J=7.5 Hz, 1H), 7.59-7.61 (m, 5H), 7.74 (t, J=8.5Hz, 1H), 7.87 (d, J=8.0 Hz, 1H), 8.01 (d, J=8.0 Hz, 1H), 8.25 (d, J=8.0Hz, 1H), 8.65 (d, J=8.0 Hz, 1H).

By train sublimation, 3.9 g of the obtained pale yellow solid waspurified. The purification by sublimation was carried out under apressure of 3.8 Pa, with a flow rate of argon gas of 15 mL/min, at atemperature of 275° C., and for 15 hours. After the purification bysublimation, 2.1 g of the target yellow solid was obtained at acollection rate of 72%.

Next, the ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as “absorption spectrum”) and emission spectrum of a toluenesolution and a solid thin film of BBABnf(8) were measured. Themeasurement was performed with a device and a method similar to thosefor the measurement in Example 1. FIG. 40 shows the measurement resultsof the absorption and emission spectra of the obtained toluene solutionand FIG. 41 shows the measurement results of the absorption and emissionspectra of the obtained thin film.

From FIG. 40, the toluene solution of BBABnf(8) has an absorption peakat around 337 nm, and an emission peak at 410 nm (excitation wavelength:337 nm).

From FIG. 41, the thin film of BBABnf(8) has an absorption peak ataround 370 nm, and an emission peak at 431 nm (excitation wavelength:358 nm).

Example 7

In this example, light-emitting elements 4 and 5 of one embodiment ofthe present invention, which are described in Embodiment 1, will bedescribed. Structural formulae of organic compounds used for thelight-emitting elements 4 and 5 are shown below.

(Method for Fabricating Light-Emitting Element 4)

First, a film of indium tin oxide containing silicon oxide (ITSO) wasformed over a glass substrate by a sputtering method, so that the anode101 was formed. The thickness thereof was 70 nm and the electrode areawas 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over thesubstrate, a surface of the substrate was washed with water and baked at200° C. for 1 hour; then UV ozone treatment was performed for 370seconds.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate was cooled down for about 30 minutes.

Next, the substrate provided with the anode 101 was fixed to a substrateholder provided in the vacuum evaporation device such that the side onwhich the anode 101 was formed faced downward. Then,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN) represented by Structural Formula (i) was deposited to athickness of 5 nm over the anode 101 by an evaporation method usingresistance heating, whereby the hole-injection layer 111 was formed.

Next, 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB)represented by Structural Formula (ix) was deposited to a thickness of10 nm over the hole-injection layer 111 by evaporation, whereby thefirst hole-transport layer 112-1 was formed;N,N-di(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation:BBABnf(6)), which is the organic compound of one embodiment of thepresent invention represented by Structural Formula (229), was depositedto a thickness of 10 nm over the first hole-transport layer 112-1 byevaporation, whereby the second hole-transport layer 112-2 was formed;and 3,6-bis[4-(2-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation:βNP2PC)) represented by Structural Formula (x) was deposited to athickness of 10 nm over the second hole-transport layer 112-2 byevaporation, whereby the third hole-transport layer 112-3 was formed.

After that, the light-emitting layer 113 was formed by co-evaporation of7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) represented by Structural Formula (iv) andN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn) represented by Structural Formula (v) ina weight ratio of 1:0.03 (=cgDBCzPA: 1,6mMemFLPAPrn) to a thickness of25 nm.

Then, over the light-emitting layer 113, cgDBCzPA was deposited to athickness of 10 nm by evaporation, and bathophenanthroline(abbreviation: BPhen) represented by Structural Formula (vi) wasdeposited to a thickness of 15 nm by evaporation, whereby theelectron-transport layer 114 was formed.

After the formation of the electron-transport layer 114, lithiumfluoride (LiF) was deposited to a thickness of 1 nm by evaporation toform the electron-injection layer 115. Then, aluminum was deposited to athickness of 200 nm by evaporation to form the cathode 102. Thus, thelight-emitting element 4 of this example was fabricated.

(Method for Fabricating Light-Emitting Element 5)

The light-emitting element 5 was formed in the same manner as thelight-emitting element 4 except that the second hole-transport layer112-2 was formed usingN,N-di(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation:BBABnf(8)) instead of BBABnf(6).

The element structures of the light-emitting elements 4 and 5 are shownin the following table.

TABLE 5 Hole- Light- injection Hole-transport layer emittingElectron-transport Electron- layer 1 2 3 layer layer injection layer 5nm 10 nm 10 nm 10 nm 25 nm 10 nm 15 nm 1 nm HAT-CN NPB *2 βNP2PCcgDBCzPA:1, cgDBCzPA BPhen LiF 6mMemFLPAPrn (1:0.03) *2 Light-emittingelement 4: BBABnf(6), Light-emitting element 5: BBABnf(8)

The light-emitting elements 4 and 5 were sealed using a glass substratein a glove box containing a nitrogen atmosphere so as not to be exposedto the air (specifically, a sealing material was applied to surround theelement and UV treatment and heat treatment at 80° C. for 1 hour wereperformed at the time of sealing). Then, the initial characteristics andreliability of the light-emitting elements were measured. Note that themeasurements were performed at room temperature (in an atmosphere keptat 25° C.).

FIG. 42 shows the luminance-current density characteristics of thelight-emitting elements 4 and 5. FIG. 43 shows the currentefficiency-luminance characteristics of the light-emitting elements 4and 5. FIG. 44 shows the luminance-voltage characteristics of thelight-emitting elements 4 and 5. FIG. 45 shows the current-voltagecharacteristics of the light-emitting elements 4 and 5. FIG. 46 showsthe external quantum efficiency-luminance characteristics of thelight-emitting elements 4 and 5. FIG. 47 shows the emission spectrum ofthe light-emitting elements 4 and 5. Table 6 shows the maincharacteristics of the light-emitting elements 4 and 5 at around 1000cd/m².

TABLE 6 External Current Current quantum Voltage Current densityefficiency efficiency (V) (mA) (mA/cm²) Chromaticity x Chromaticity y(cd/A) (%) Light-emitting 3.30 0.30 7.60 0.14 0.17 13.4 11.7 element 4Light-emitting 3.30 0.31 7.74 0.14 0.15 13.0 11.5 element 5

It was found from FIGS. 42 to 46 and Table 6 that the light-emittingelements 4 and 5 of one embodiment of the present invention are bluelight-emitting elements with favorable efficiency and a low drivingvoltage.

FIG. 48 shows driving time-dependent change in luminance of thelight-emitting elements under the conditions where the current value wasset to 2 mA and the current density was constant. As shown in FIG. 48,the light-emitting elements 4 and 5 maintained 85% or more of theinitial luminance after 100-hour-driving and were found to belong-lifetime light-emitting elements with an extremely small reductionin luminance over driving time.

Example 8

In this example, light-emitting elements 6 and 7 of one embodiment ofthe present invention, which are described in Embodiment 1, will bedescribed. Structural formulae of organic compounds used for thelight-emitting elements 6 and 7 are shown below.

(Method for Fabricating Light-Emitting Element 6)

First, a film of indium tin oxide containing silicon oxide (ITSO) wasformed over a glass substrate by a sputtering method, so that the anode101 was formed. The thickness thereof was 70 nm and the electrode areawas 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over thesubstrate, a surface of the substrate was washed with water and baked at200° C. for 1 hour; then UV ozone treatment was performed for 370seconds.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate was cooled down for about 30 minutes.

Next, the substrate provided with the anode 101 was fixed to a substrateholder provided in the vacuum evaporation device such that the side onwhich the anode 101 was formed faced downward. Then,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN) represented by Structural Formula (i) was deposited to athickness of 5 nm over the anode 101 by an evaporation method usingresistance heating, whereby the hole-injection layer 111 was formed.

Next, 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB)represented by Structural Formula (ix) was deposited to a thickness of20 nm over the hole-injection layer 111 by evaporation, whereby thefirst hole-transport layer 112-1 was formed; andN,N-di(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation:BBABnf(6)), which is the organic compound of one embodiment of thepresent invention represented by Structural Formula (229), was depositedto a thickness of 10 nm over the first hole-transport layer 112-1 byevaporation, whereby the second hole-transport layer 112-2 was formed.

After that, the light-emitting layer 113 was formed by co-evaporation of7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) represented by Structural Formula (iv) andN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn) represented by Structural Formula (v) ina weight ratio of 1:0.03 (=cgDBCzPA: 1,6mMemFLPAPrn) to a thickness of25 nm.

Then, over the light-emitting layer 113, cgDBCzPA was deposited to athickness of 10 nm by evaporation, and bathophenanthroline(abbreviation: BPhen) represented by Structural Formula (vi) wasdeposited to a thickness of 15 nm by evaporation, whereby theelectron-transport layer 114 was formed.

After the formation of the electron-transport layer 114, lithiumfluoride (LiF) was deposited to a thickness of 1 nm by evaporation toform the electron-injection layer 115. Then, aluminum was deposited to athickness of 200 nm by evaporation to form the cathode 102. Thus, thelight-emitting element 6 of this example was fabricated.

(Method for Fabricating Light-Emitting Element 7)

The light-emitting element 7 was formed in the same manner as thelight-emitting element 6 except that the second hole-transport layer112-2 was formed usingN,N-di(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation:BBABnf(8)) instead of BBABnf(6).

The element structures of the light-emitting elements 6 and 7 are shownin the following table.

TABLE 7 Hole- Light- injection Hole-transport emittingElectron-transport Electron- layer layer layer layer injection layer 5nm 20 nm 10 nm 25 nm 10 nm 15 nm 1 nm HAT-CN NPB *3 cgDBCzPA:1, cgDBCzPABPhen LiF 6mMemFLPAPrn (1:0.03) *3 Light-emitting element 6: BBABnf(6),Light-emitting element 7: BBABnf(8)

The light-emitting elements 6 and 7 were sealed using a glass substratein a glove box containing a nitrogen atmosphere so as not to be exposedto the air (specifically, a sealing material was applied to surround theelement and UV treatment and heat treatment at 80° C. for 1 hour wereperformed at the time of sealing). Then, the initial characteristics andreliability of the light-emitting elements were measured. Note that themeasurements were performed at room temperature (in an atmosphere keptat 25° C.).

FIG. 49 shows the luminance-current density characteristics of thelight-emitting elements 6 and 7. FIG. 50 shows the currentefficiency-luminance characteristics of the light-emitting elements 6and 7. FIG. 51 shows the luminance-voltage characteristics of thelight-emitting elements 6 and 7. FIG. 52 shows the current-voltagecharacteristics of the light-emitting elements 6 and 7. FIG. 53 showsthe external quantum efficiency-luminance characteristics of thelight-emitting elements 6 and 7. FIG. 54 shows the emission spectrum ofthe light-emitting elements 6 and 7. Table 8 shows the maincharacteristics of the light-emitting elements 6 and 7 at around 1000cd/m².

TABLE 8 External Current Current quantum Voltage Current densityefficiency efficiency (V) (mA) (mA/cm²) Chromaticity x Chromaticity y(cd/A) (%) Light-emitting 3.10 0.33 8.27 0.14 0.16 12.0 10.1 element 6Light-emitting 3.10 0.31 7.80 0.14 0.15 11.9 10.9 element 7

It was found from FIGS. 49 to 54 and Table 8 that the light-emittingelements 6 and 7 of one embodiment of the present invention are bluelight-emitting elements with favorable efficiency and a low drivingvoltage.

Example 9

In this example, a light-emitting element 8 of one embodiment of thepresent invention, which is described in Embodiment 1, will bedescribed. Structural formulae of organic compounds used for thelight-emitting element 8 are shown below.

(Method for Fabricating Light-Emitting Element 8)

First, a film of indium tin oxide containing silicon oxide (ITSO) wasformed over a glass substrate by a sputtering method, so that the anode101 was formed. The thickness thereof was 70 nm and the electrode areawas 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over thesubstrate, a surface of the substrate was washed with water and baked at200° C. for 1 hour; then UV ozone treatment was performed for 370seconds.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate was cooled down for about 30 minutes.

Next, the substrate provided with the anode 101 was fixed to a substrateholder provided in the vacuum evaporation device such that the side onwhich the anode 101 was formed faced downward. Then,N,N-bis(biphenyl-4-yl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BBABnf), which is the organic compound of one embodimentof the present invention represented by Structural Formula (146), and1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation:F6-TCNNQ), which is represented by Structural Formula (xi), weredeposited to a thickness of 10 nm over the anode 101 by co-evaporationin a weight ratio of 2:1 (=BBABnf: F6-TCNNQ), whereby the hole-injectionlayer 111 was formed.

Next, BBABnf was deposited to a thickness of 10 nm over thehole-injection layer 111 by evaporation, whereby the firsthole-transport layer 112-1 was formed; and3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn)represented by Structural Formula (vii) was deposited to a thickness of20 nm over the first hole-transport layer 112-1 by evaporation, wherebythe second hole-transport layer 112-2 was formed.

After that, the light-emitting layer 113 was formed by co-evaporation of7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) represented by Structural Formula (iv) andN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn) represented by Structural Formula (v) ina weight ratio of 1:0.03 (=cgDBCzPA: 1,6mMemFLPAPrn) to a thickness of25 nm.

Then, over the light-emitting layer 113,2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II), which is represented by StructuralFormula (xii), was deposited to a thickness of 10 nm by evaporation, and2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation:NBPhen) represented by Structural Formula (xiii) was deposited to athickness of 15 nm by evaporation, whereby the electron-transport layer114 was formed.

After the formation of the electron-transport layer 114, lithiumfluoride (LiF) was deposited to a thickness of 1 nm by evaporation toform the electron-injection layer 115. Then, aluminum was deposited to athickness of 200 nm by evaporation to form the cathode 102. Thus, thelight-emitting element 8 of this example was fabricated.

The element structure of the light-emitting element 8 is shown in thefollowing table.

TABLE 9 Hole- Light- Electron- injection emitting injection layerHole-transport layer layer Electron-transport layer layer 10 nm 10 nm 20nm 25 nm 10 nm 15 nm 1 nm BBABnf:F6- BBABnf PCPPn cgDBCzPA:1,2mDBTBPDBq- NBPhen LiF TCNNQ 6mMemFLPAPrn II (1:0.5) (1:0.03)

The light-emitting element 8 was sealed using a glass substrate in aglove box containing a nitrogen atmosphere so as not to be exposed tothe air (specifically, a sealing material was applied to surround theelement and UV treatment and heat treatment at 80° C. for 1 hour wereperformed at the time of sealing). Then, the initial characteristics andreliability of the light-emitting element were measured. Note that themeasurements were performed at room temperature (in an atmosphere keptat 25° C.).

FIG. 55 shows the luminance-current density characteristics of thelight-emitting element 8. FIG. 56 shows the current efficiency-luminancecharacteristics of the light-emitting element 8. FIG. 57 shows theluminance-voltage characteristics of the light-emitting element 8. FIG.58 shows the current-voltage characteristics of the light-emittingelement 8. FIG. 59 shows the external quantum efficiency-luminancecharacteristics of the light-emitting element 8. FIG. 60 shows theemission spectrum of the light-emitting element 8. Table 10 shows themain characteristics of the light-emitting element 8 at around 1000cd/m².

TABLE 10 External Current Current quantum Voltage Current densityefficiency efficiency (V) (mA) (mA/cm²) Chromaticity x Chromaticity y(cd/A) (%) Light- 3.30 0.31 7.65 0.14 0.16 14.2 12.2 emitting element 8

It was found from FIGS. 55 to 60 and Table 10 that the light-emittingelement 8 of one embodiment of the present invention is a bluelight-emitting element with favorable efficiency and a low drivingvoltage.

FIG. 61 shows driving time-dependent change in luminance of thelight-emitting element under the conditions where the current value wasset to 2 mA and the current density was constant. As shown in FIG. 61,the light-emitting element 8 maintained 90% or more of the initialluminance after 100-hour-driving and were found to be long-lifetimelight-emitting element with an extremely small reduction in luminanceover driving time. This application is based on Japanese PatentApplication serial No. 2016-016262 filed with Japan Patent Office onJan. 29, 2016, the entire contents of which are hereby incorporated byreference.

EXPLANATION OF REFERENCE

101: anode 102: cathode 103: EL layer 111: hole-injection layer 112:hole-transport layer 112-1: first hole-transport layer 112-2: secondhole-transport layer 112-3: third hole-transport layer 113:light-emitting layer 114: electron-transport layer 115:electron-injection layer 116: charge-generation layer 117: p-type layer118: electron-relay layer 119: electron-injection buffer layer 400:substrate 401: anode 403: EL layer 404: cathode 405: sealing material406: sealing material 407: sealing substrate 412: pad 420: IC chip 501:anode 502: cathode 511: first light-emitting unit 512: secondlight-emitting unit 513: charge-generation layer 601: driver circuitportion (source line driver circuit) 602: pixel portion 603: drivercircuit portion (gate line driver circuit) 604: sealing substrate 605:sealing material 607: space 608: wiring 609: FPC (flexible printedcircuit) 610: element substrate 611: switching FET 612: currentcontrolling FET 613: anode 614: insulator 616: EL layer 617: cathode618: light-emitting element 730: insulating film 770: planarizationinsulating film 772: conductive film 782: light-emitting element 783:droplet discharge apparatus 784: droplet 785: layer 786: EL layer 788:conductive film 901: housing 902: liquid crystal layer 903: backlightunit 904: housing 905: driver IC 906: terminal 951: substrate 952:electrode 953: insulating layer 954: partition layer 955: EL layer 956:electrode 1001: substrate 1002: base insulating film 1003: gateinsulating film 1006: gate electrode 1007: gate electrode 1008: gateelectrode 1020: first interlayer insulating film 1021: second interlayerinsulating film 1022: electrode 1024W: anode 1024R: anode 1024G: anode1024B: anode 1025: partition 1028: EL layer 1029: cathode 1031: sealingsubstrate 1032: sealing material 1033: transparent base material 1034R:red coloring layer 1034G: green coloring layer 1034B: blue coloringlayer 1035: black matrix 1036: overcoat layer 1037: third interlayerinsulating film 1040: pixel portion 1041: driver circuit portion 1042:peripheral portion 1400: droplet discharge apparatus 1402: substrate1403: droplet discharge means 1404: imaging means 1405: head 1406:dotted line 1407: control means 1408: storage medium 1409: imageprocessing means 1410: computer 1411: marker 1412: head 1413: materialsupply source 1414: material supply source 1415: material supply source1416: head 2001: housing 2002: light source 3001: lighting device 5000:display region 5001: display region 5002: display region 5003: displayregion 5004: display region 5005: display region 7101: housing 7103:display portion 7105: stand 7107: display portion 7109: operation key7110: remote controller 7201: main body 7202: housing 7203: displayportion 7204: keyboard 7205: external connection port 7206: pointingdevice 7210: second display portion 7301: housing 7302: housing 7303:joint portion 7304: display portion 7305: display portion 7306: speakerportion 7307: recording medium insertion portion 7308: LED lamp 7309:operation key 7310: connection terminal 7311: sensor 7401: housing 7402:display portion 7403: operation button 7404: external connection port7405: speaker 7406: microphone 7400: mobile phone 9033: clasp 9034:switch 9035: power switch 9036: switch 9038: operation switch 9310:portable information terminal 9311: display panel 9312: display region9313: hinge 9315: housing 9630: housing 9631: display portion 9631 a:display portion 9631 b: display portion 9632 a: touchscreen region 9632b: touchscreen region 9633: solar cell 9634: charge and dischargecontrol circuit 9635: battery 9636: DCDC converter 9637: operation kay9638: converter 9639: button

The invention claimed is:
 1. A light-emitting element comprising: ananode; a cathode; and an EL layer including a hole-injection layer,wherein the EL layer is positioned between the anode and the cathode,wherein the EL layer includes a light-emitting layer and ahole-transport layer, wherein the hole-transport layer is positionedbetween the light-emitting layer and the anode, wherein thehole-injection layer is in contact with the anode and the hole-transportlayer, wherein the hole-injection layer includes an organic compoundhaving an acceptor property, and wherein the hole-transport layerincludes an organic compound represented by General Formula (G1),

wherein R¹ to R⁸ independently represent any one of hydrogen, ahydrocarbon group having 1 to 6 carbon atoms, a cyclic hydrocarbon grouphaving 3 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,a cyano group, halogen, a haloalkyl group having 1 to 6 carbon atoms,and a substituted or unsubstituted aromatic hydrocarbon group having 6to 60 carbon atoms, wherein one of A and B represents a grouprepresented by General Formula (g3) and the other represents any one ofhydrogen, a cyclic hydrocarbon group having 3 to 6 carbon atoms, analkoxy group having 1 to 6 carbon atoms, a cyano group, halogen, ahaloalkyl group having 1 to 6 carbon atoms, a hydrocarbon group having 1to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms,

wherein Ar⁵ and Ar⁶ independently represent a substituted orunsubstituted divalent aromatic hydrocarbon group having 6 to 54 carbonatoms, wherein n and m independently represent 0 to 2, wherein the sumof carbon atoms of Ar^(a) and Ar⁵ is less than or equal to 60, whereinthe sum of carbon atoms of Ar⁴ and Ar⁶ is less than or equal to 60,wherein Ar³ and Ar⁴ independently represent any one of an unsubstitutedaromatic hydrocarbon group having 6 to 60 carbon atoms, a substituted orunsubstituted benzonaphthofuranyl group, a substituted or unsubstituteddinaphthofuranyl group, and a group represented by General Formula (g2),

wherein R¹¹ to R¹⁸ independently represent any one of hydrogen, ahydrocarbon group having 1 to 6 carbon atoms, a cyclic hydrocarbon grouphaving 3 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,a cyano group, halogen, a haloalkyl group having 1 to 6 carbon atoms,and a substituted or unsubstituted aromatic hydrocarbon group having 6to 60 carbon atoms, wherein one of Z¹ and Z² is bonded to a nitrogenatom in General Formula (g3) and the other represents any one ofhydrogen, a cyclic hydrocarbon group having 3 to 6 carbon atoms, analkoxy group having 1 to 6 carbon atoms, a cyano group, halogen, ahaloalkyl group having 1 to 6 carbon atoms, a hydrocarbon group having 1to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms, wherein the organiccompound does not have two or more substituted or unsubstituted amineskeletons, wherein the hole-transport layer includes a first layer, asecond layer, and a third layer, wherein the first layer is positionedbetween the hole-injection layer and the second layer, wherein the thirdlayer is positioned between the second layer and the light-emittinglayer, wherein the first layer is in contact with the hole-injectionlayer, wherein the third layer is in contact with the light-emittinglayer, wherein the first layer includes a first hole-transport material,wherein the second layer includes the organic compound, wherein thethird layer includes a third hole-transport material, wherein thelight-emitting layer includes a host material and a light-emittingmaterial, wherein a HOMO level of the organic compound is deeper than aHOMO level of the first hole-transport material, wherein a HOMO level ofthe host material is deeper than the HOMO level of the organic compound,and wherein a difference between the HOMO level of the organic compoundand a HOMO level of the third hole-transport material is less than orequal to 0.3 eV.
 2. The light-emitting element according to claim 1,wherein the organic compound having the acceptor property is2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene.
 3. Thelight-emitting element according to claim 1, wherein the HOMO level ofthe first hole-transport material is greater than or equal to 5.4 eV. 4.The light-emitting element according to claim 1, wherein a differencebetween the HOMO level of the first hole-transport material and the HOMOlevel of the organic compound is less than or equal to 0.3 eV, andwherein the difference between the HOMO level of the organic compoundand the HOMO level of the third hole-transport material is less than orequal to 0.2 eV.
 5. The light-emitting element according to claim 4,wherein the difference between the HOMO level of the firsthole-transport material and the HOMO level of the organic compound isless than or equal to 0.2 eV.
 6. The light-emitting element according toclaim 1, wherein the light-emitting material emits blue fluorescence. 7.The light-emitting element according to claim 1, wherein thelight-emitting material is a condensed aromatic diamine compound.
 8. Thelight-emitting element according to claim 1, wherein the light-emittingmaterial is a diaminopyrene compound.
 9. The light-emitting elementaccording to claim 1, wherein a HOMO level of the light-emittingmaterial is higher than the HOMO level of the host material, and whereinthe HOMO level of the third hole-transport material is deeper than orequal to the HOMO level of the host material.
 10. A light-emittingdevice comprising: the light-emitting element according to claim 1; anda transistor or a substrate.
 11. A light-emitting element comprising: ananode; a cathode; and an EL layer including a hole-injection layer,wherein the EL layer is positioned between the anode and the cathode,wherein the EL layer includes a light-emitting layer and ahole-transport layer, wherein the hole-transport layer is positionedbetween the light-emitting layer and the anode, wherein thehole-injection layer is in contact with the anode and the hole-transportlayer, wherein the hole-injection layer includes an organic compoundhaving an acceptor property, wherein the hole-transport layer includesan organic compound represented by General Formula (G1),

wherein R¹ to R⁸ independently represent any one of hydrogen, ahydrocarbon group having 1 to 6 carbon atoms, a cyclic hydrocarbon grouphaving 3 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,a cyano group, halogen, a haloalkyl group having 1 to 6 carbon atoms,and a substituted or unsubstituted aromatic hydrocarbon group having 6to 60 carbon atoms, wherein one of A and B represents a grouprepresented by General Formula (g3) and the other represents any one ofhydrogen, a cyclic hydrocarbon group having 3 to 6 carbon atoms, analkoxy group having 1 to 6 carbon atoms, a cyano group, halogen, ahaloalkyl group having 1 to 6 carbon atoms, a hydrocarbon group having 1to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms,

wherein Ar⁵ and Ar⁶ independently represent a substituted orunsubstituted divalent aromatic hydrocarbon group having 6 to 54 carbonatoms, wherein n represents 0 or 1, wherein m represents 1, wherein thesum of carbon atoms of Ar³ and Ar⁵ is less than or equal to 60, whereinthe sum of carbon atoms of Ar⁴ and Ar⁶ is less than or equal to 60,wherein Ar³ and Ar⁴ independently represent any one of an unsubstitutedaromatic hydrocarbon group having 6 to 60 carbon atoms, a substituted orunsubstituted benzonaphthofuranyl group, a substituted or unsubstituteddinaphthofuranyl group, and a group represented by General Formula (g2),

wherein R¹¹ to R¹⁸ independently represent any one of hydrogen, ahydrocarbon group having 1 to 6 carbon atoms, a cyclic hydrocarbon grouphaving 3 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,a cyano group, halogen, a haloalkyl group having 1 to 6 carbon atoms,and a substituted or unsubstituted aromatic hydrocarbon group having 6to 60 carbon atoms, wherein one of Z¹ and Z² is bonded to a nitrogenatom in General Formula (g3) and the other represents any one ofhydrogen, a cyclic hydrocarbon group having 3 to 6 carbon atoms, analkoxy group having 1 to 6 carbon atoms, a cyano group, halogen, ahaloalkyl group having 1 to 6 carbon atoms, a hydrocarbon group having 1to 6 carbon atoms, and a substituted or unsubstituted aromatichydrocarbon group having 6 to 60 carbon atoms, wherein the organiccompound does not have two or more substituted or unsubstituted amineskeletons, wherein the hole-transport layer includes a first layer, asecond layer, and a third layer, wherein the first layer is positionedbetween the hole-injection layer and the second layer, wherein the thirdlayer is positioned between the second layer and the light-emittinglayer, wherein the first layer is in contact with the hole-injectionlayer, wherein the third layer is in contact with the light-emittinglayer, wherein the first layer includes a first hole-transport material,wherein the second layer includes the organic compound, wherein thethird layer includes a third hole-transport material, wherein thelight-emitting layer includes a host material and a light-emittingmaterial, wherein a HOMO level of the organic compound is deeper than aHOMO level of the first hole-transport material, wherein a HOMO level ofthe host material is deeper than the HOMO level of the organic compound,and wherein a difference between the HOMO level of the organic compoundand a HOMO level of the third hole-transport material is less than orequal to 0.3 eV.
 12. The light-emitting element according to claim 11,wherein the HOMO level of the first hole-transport material is greaterthan or equal to 5.4 eV.
 13. The light-emitting element according toclaim 11, wherein a difference between the HOMO level of the firsthole-transport material and the HOMO level of the organic compound isless than or equal to 0.3 eV, and wherein the difference between theHOMO level of the organic compound and the HOMO level of the thirdhole-transport material is less than or equal to 0.2 eV.
 14. Thelight-emitting element according to claim 13, wherein the differencebetween the HOMO level of the first hole-transport material and the HOMOlevel of the organic compound is less than or equal to 0.2 eV.
 15. Thelight-emitting element according to claim 11, wherein the organiccompound having the acceptor property is2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene.
 16. Thelight-emitting element according to claim 11, wherein the HOMO level ofthe light-emitting material is higher than the HOMO level of the hostmaterial, and wherein a HOMO level of the third hole-transport materialis deeper than or equal to the HOMO level of the host material.
 17. Thelight-emitting element according to claim 11, wherein the light-emittingmaterial emits blue fluorescence.
 18. The light-emitting elementaccording to claim 11, wherein the light-emitting material is acondensed aromatic diamine compound.
 19. The light-emitting elementaccording to claim 11, wherein the light-emitting material is adiaminopyrene compound.
 20. A light-emitting device comprising: thelight-emitting element according to claim 11; and a transistor or asubstrate.